As we know that ,
Replace his nearly all many pets :- nearly all his many pets

Correct Option: C

As we know that ,
Replace his nearly all many pets :- nearly all his many pets
Therefore , his nearly all many pets is replaced by nearly all his many pets in above given sentence .

As we know that ,
drop into position in a chair is correct .
Grandfather is often so tired that he drops in his armchair. is correct sentence .

Correct Option: D

As we know that ,
drop into position in a chair is correct .
Grandfather is often so tired that he drops in his armchair is correct sentence .
Thus , No improvement will be in above given sentence .

As we know that ,
Replace the word hanging with a thread :-Hang by a thread/hair
Hang by a thread/hair means: to be in great danger.

Correct Option: B

As we know that ,
Replace the word hanging with a thread :-Hang by a thread/hair
Hang by a thread/hair means: to be in great danger.
Hence , hanging with a thread is replaced by Hang by a thread/hair in above given question .

As per the given above sentence , we can say that
The court was forced to respect the profundity of the learned judge’s knowledge is correct sentence .

Correct Option: D

As per the given above sentence , we can say that
The court was forced to respect the profundity of the learned judge’s knowledge is correct sentence .
Hence , No improvement will be in above given sentence .So , option D is correct .

As per the given above sentence , we can say that
Replace was in the end of his tether :- Be at the end of your tether
Be at the end of your tether means :- to feel that you cannot deal with a difficult situation any more because you are too tired, worried etc.

Correct Option: C

As per the given above sentence , we can say that
Replace was in the end of his tether :- Be at the end of your tether
Be at the end of your tether means :- to feel that you cannot deal with a difficult situation any more because you are too tired, worried etc.
Therefore , in is replaced by at in above given sentence .