21.

  1. for
  2. to
  3. with
  4. on

22.

  1. concerning
  2. concern
  3. being concerned
  4. concerned

23.

  1. imitate
  2. simulate
  3. impersonate
  4. copy

24.

  1. From then on
  2. From now on
  3. By now
  4. By then

25.

  1. considerable
  2. considerate
  3. considering
  4. considered

26.

  1. for
  2. in
  3. with
  4. on

27.

  1. on the part of
  2. on the basis of
  3. on the track of
  4. on the verge of

28.

  1. to
  2. for
  3. on
  4. in

29.

  1. as for
  2. as to
  3. as
  4. for

30.

  1. acquiring
  2. requiring
  3. sustaining
  4. retaining

(Reference keys.)