fronted preposition + relative pronoun

Wh-relatives can be preceded by a preposition unlike ‘that’ or ‘zero’ relatives.  For example:

• This is the thing which I am interested in.  (stranded preposition)
• This is the thing in which I am interested. (fronted preposition)
• This is the thing that I am interested in. (stranding)
• This is the thing I am interested in. (‘zero’ relative pronoun and stranding)

In the English Grammar Profile, B2 point 12 in the category of PREPOSITIONs is defined as:

preposition + relative pronoun as complement, to avoid preposition stranding, often in formal contexts.

The EGP examples include:

vacancy_NN1 in_II which_DDQ I_PPIS1 am_VBM very_RG interested_JJ ._.

club_NN1 of_IO which_DDQ you_PPY are_VBR  the_AT secretary_NN1 ._.

someone_PN1 to_II whom_PNQO  they_PPHS2 can_VM talk_VVI ._.

‘Whom’ is listed at B2 in the English Vocabulary Profile with the following examples:

I met a man with whom I used to work.
There were 500 passengers, of whom 121 drowned.
To whom do you wish to speak?
This is just to let you know with whom I worked.

A search on the iWeb corpus for _n _i wh* _p _v gives us:

(*note not everything below will qualify as avoiding stranding)

1 WAYS IN WHICH YOU CAN 5216
2 WORLD IN WHICH WE LIVE 2711
3 FROM WHAT I CAN 2656
4 FROM WHAT I HAVE 2506
5 FROM WHAT I UNDERSTAND 2388
6 WAYS IN WHICH WE CAN 1955
7 PART OF WHAT WE DO 1879
8 ORDER IN WHICH THEY ARE 1757
9 PART OF WHO WE ARE 1711
10 PART OF WHO I AM 1599
11 IDEA OF WHAT YOU WANT 1541
12 HEART OF WHAT WE DO 1302

PURPOSE FOR WHICH IT WAS

  Sarajevo Times

As a reason for the abolition of the Fund, the Federal Government stated that in recent years the Fund has less and less achieved the goal and purpose for which it was established in 2006.

14 UNDERSTANDING OF WHAT IT MEANS 1271
15 COMMUNITIES IN WHICH WE OPERATE 1225
16 TO WHOM IT MAY 1165
17 WAYS IN WHICH THEY CAN 1089
18 ORDER IN WHICH THEY WERE 1064
19 PART OF WHO YOU ARE 950
20 IDEA OF WHAT YOU CAN 945
21 COMMUNITIES IN WHICH WE LIVE 933
22 IDEA OF WHAT YOU ARE 913
23 LIMIT TO WHAT YOU CAN 905
24 IDEA OF WHAT IT IS 830
25 ORDER IN WHICH THEY APPEAR 760
26 COMMUNITIES IN WHICH THEY LIVE 757
27 EXAMPLE OF WHAT I MEAN 753
28 WAY IN WHICH IT IS 744
29 UNDERSTANDING OF WHAT IT TAKES 743
30 FOR WHAT IT IS 733
31 WORLD IN WHICH THEY LIVE 728
32 WAY IN WHICH YOU CAN 714
33 MANNER IN WHICH IT IS 713
34 UNDERSTANDING OF WHAT IT IS 686
35 PART OF WHAT I DO 683
36 PURPOSES FOR WHICH IT WAS 662
37 PURPOSE FOR WHICH IT IS 659
38 WAY IN WHICH THEY ARE 654
39 MANNER IN WHICH THEY ARE 642
40 SENSE OF WHO YOU ARE 635
41 IDEA OF WHAT THEY ARE 630
42 FROM WHAT I KNOW 627
43 LIKE WHAT YOU SEE 592
44 EXAMPLE OF WHAT YOU CAN 591
45 FROM WHAT I READ 589
46 MANNER IN WHICH IT WAS 586
47 CONTEXT IN WHICH IT IS 578
48 ATTENTION TO WHAT YOU ARE 567
49 IDEA OF WHAT THEY WANT 557
50 CORE OF WHAT WE DO 556
51 WAYS IN WHICH THEY ARE 550
52 PART OF WHO THEY ARE 522
53 WAY IN WHICH WE CAN 516
54 EXTENT TO WHICH IT IS 506
55 IDEA OF WHAT YOU NEED 501
56 FROM WHAT I REMEMBER 500
57 EASE WITH WHICH YOU CAN 500
58 EXTENT TO WHICH THEY ARE 498
59 OPPOSITE OF WHAT YOU WANT 497
60 WAYS IN WHICH IT CAN 496
61 PASSION FOR WHAT THEY DO 495
62 IDEA OF WHAT I WANTED 475
63 SENSE OF WHO THEY ARE 471
64 POSITION FOR WHICH YOU ARE 468
65 QUESTION OF WHETHER IT IS 468
66 EXAMPLES OF WHAT YOU CAN 467
67 LOT OF WHAT WE DO 463
68 LOOK AT WHAT YOU CAN 458

PERSON TO WHOM IT IS

  Free Press Journal

… and cannot be used by anybody other than the person to whom it is sold (the lawyer or the registered clerk as the case may be).

70 COMMUNITIES IN WHICH WE WORK 455
71 LIST OF WHAT YOU NEED 445
72 SOCIETY IN WHICH WE LIVE 438
73 ORDER OF WHEN THEY WERE 430
74 PEOPLE FOR WHO THEY ARE 427
75 PART OF WHAT IT MEANS 426
76 YEAR IN WHICH THEY ARE 426
77 TIMES IN WHICH WE LIVE 424
78 FROM WHAT I GATHER 423
79 PAY FOR WHAT YOU USE 421
80 SENSE OF WHO WE ARE 407
81 ENVIRONMENT IN WHICH THEY ARE 404
82 PRIDE IN WHAT THEY DO 404
83 LOOK AT WHAT WE HAVE 402
84 CONTEXT IN WHICH IT WAS 395
85 CONTEXT IN WHICH THEY ARE 395
86 IDEA OF WHAT IT MEANS 395
87 TRACK OF WHERE YOU ARE 395
88 IDEA OF WHAT I WANT 393
89 WAY IN WHICH IT WAS 392
90 COUNTRY IN WHICH YOU ARE 388
91 UNDERSTANDING OF WHAT THEY ARE 386
92 DESPITE WHAT YOU MAY 383
93 ENVIRONMENT IN WHICH THEY CAN 383
94 DEFINITION OF WHAT IT MEANS 381
95 PASSION FOR WHAT YOU DO 378
96 CORE OF WHO WE ARE 374
97 PRIDE IN WHAT WE DO 371
98 WAYS IN WHICH IT IS 367
99 PURPOSE FOR WHICH THEY WERE 357
100 COMMUNITIES IN WHICH IT OPERATES 356

With a pronoun preceding:

1 IT FOR WHAT IT IS 3589
2 THEM FOR WHAT THEY ARE 1184
3 YOU FOR WHO YOU ARE 1145
4 US TO WHERE WE ARE 935
5 ME TO WHERE I AM 926
6 IT FOR WHAT IT WAS 746
7 YOU TO WHERE YOU WANT 639
8 YOU FOR WHAT YOU DO 594
9 ME OF WHEN I WAS 592
10 YOU TO WHERE YOU ARE 474
11 YOU TO WHERE YOU NEED 390
12 YOU FOR WHAT YOU ARE 387
13 IT TO WHERE YOU WANT 383
14 YOU WITH WHAT YOU NEED 366
15 YOU FOR WHAT YOU HAVE 317
16 THEM TO WHERE THEY ARE 307
17 HIM FOR WHAT HE DID 284
18 HIM TO WHERE HE IS 263
19 YOU THROUGH WHAT YOU NEED 251
20 HIM FOR WHAT HE IS 243
21 IT TO WHERE IT IS 230
22 YOU FROM WHERE YOU ARE 218
23 YOU WITH WHATEVER YOU NEED 207
24 HIM FOR WHAT HE HAS 202
25 THEM FOR WHAT THEY WERE 200
26 YOU FOR WHAT YOU DID 190
27 ME TO WHERE I CAN 187
28 IT TO WHATEVER YOU WANT 184
29 SOMEONE WITH WHOM YOU HAVE 172
30 YOU TO WHERE YOU CAN 170
31 ONE IN WHICH YOU ARE 167
32 ME INTO WHO I AM 156
33 SOMEONE WITH WHOM YOU CAN 156
34 THEM FOR WHAT THEY DID 153
35 THEM FOR WHAT THEY HAVE 147
36 THEM WITH WHAT THEY NEED 138
37 THEM FOR WHAT THEY DO 133
38 THEM TO WHERE THEY NEED 129
39 IT TO WHERE YOU CAN 125
40 HIM FOR WHAT HE WAS 113
41 IT INTO WHAT IT IS 111
42 HER TO WHERE SHE IS 110
43 US TO WHERE WE WANT 110
44 ME FOR WHAT I AM 107
45 HER FOR WHAT SHE IS 106
46 ME TO WHERE I WANT 105
47 SOMETHING ABOUT WHO YOU ARE 102

NONE OF WHICH I HAVE

  Science Fiction

The book was written by Joe Schreiber, who has written a few horror novels before, none of which I have read.

49 IT TO WHERE IT NEEDS 102
50 IT TO WHAT YOU WANT 101
51 HIM FOR WHAT HE HAD 101
52 ONE IN WHICH IT IS 98
53 US OF WHO WE ARE 98
54 US TO WHERE WE NEED 94
55 THEM TO WHERE YOU WANT 93
56 THEM ABOUT WHAT THEY ARE 93
57 ME FOR WHAT I DID 92
58 ME OF WHY I LOVE 90
59 HER FOR WHAT SHE DID 88
60 ONE IN WHICH YOU CAN 85
61 THEM TO WHERE THEY WANT 84
62 IT TO WHERE IT WAS 83
63 YOU ABOUT WHAT YOU ARE 83
64 ME FOR WHAT I WAS 82
65 ONE IN WHICH WE ARE 81
66 YOU ON WHAT YOU NEED 81
67 US INTO WHO WE ARE 74
68 SOMEONE WITH WHOM THEY CAN 73
69 IT TO WHAT IT IS 71
70 SOMEONE WITH WHOM YOU ARE 70
71 US FOR WHAT WE ARE 69
72 NONE OF WHICH I CAN 68
73 IT TO WHEREVER YOU WANT 68
74 SOMEONE FOR WHO THEY ARE 68
75 THEM FROM WHERE THEY ARE 67
76 IT TO WHATEVER YOU LIKE 67
77 IT WITH WHATEVER YOU WANT 67
78 ME FROM WHEN I WAS 66
79 ME FOR WHAT I HAVE 66
80 US ABOUT WHAT YOU DO 66
81 THEM WITH WHAT THEY WANT 65
82 YOU ON WHAT YOU CAN 65
83 THEM TO WHERE THEY WERE 64
84 IT WITH WHAT YOU HAVE 64
85 IT TO WHERE YOU ARE 62
86 ONE IN WHICH THEY ARE 62
87 ONE IN WHICH HE WAS 61
88 ME OF WHEN I USED 61
89 ME TO WHERE I COULD 60
90 ME FOR WHAT I HAD 60
91 IT TO WHERE I AM 60
92 EVERYONE FOR WHO THEY ARE 60
93 US WITH WHAT WE NEED 60
94 YOURSELF WITH WHAT YOU CAN 60
95 IT AS WHAT IT IS 59
96 YOU ON WHAT YOU SHOULD 59
97 YOURSELF ABOUT WHAT YOU WANT 59
98 IT FOR WHAT YOU WILL 58
99 ME TO WHERE I NEED 57
100 YOU WITH WHAT YOU WANT 57

B1 vocabulary:

appear, attention, despite, environment, limit, none, operate, operates, position, purpose, purposes, sense, society, track, whatever, wherever, whether

This point should probably cover questions.  If the wh-word or the phrase it is part of is the complement of a preposition, in formal style
the preposition moves to the front together with its complement:

To what companies does it apply?