Here, has widened ..... should be used.
Widen = to become wider; larger in degree.

Correct Option: D

Here, has widened ..... should be used.
Widen = to become wider; larger in degree.
Therefore , No improvement will be in above given sentence . So , option D is correct answer .

As we know that ,
Present Perfect Continuous should be used as the work continued in the past and still continues.
Replace the clause will be able to use :- have been able to use

Correct Option: A

As we know that ,
Present Perfect Continuous should be used as the work continued in the past and still continues.
Replace the clause will be able to use :- have been able to use
Hence , required answer will be option A .

As we know that ,
All the time = very often; frequently.
She cries all the time is correct sentence already .

Correct Option: D

As we know that ,
All the time = very often; frequently.
She cries all the time is correct sentence already .
Thus , No improvement will be in above given sentence .So , option D is correct .

As we know that ,
For singular subject (the firm), it should be used.
Correct sentence will be :-
The firm buys frozen seafood in bulk, packs it into smaller pouches and then they it sells them to the local grocery stores.

Correct Option: A

As we know that ,
For singular subject (the firm), it should be used.
Correct sentence will be :-
The firm buys frozen seafood in bulk, packs it into smaller pouches and then they it sells them to the local grocery stores.
Therefore , Option A will be required answer .

Arrangement of words :-
Replace the sentence How, is beyond my understanding, the boy could fall into the ditch :- How the boy could fall into the ditch is beyond my understanding

Correct Option: A

Arrangement of words :-
Replace the sentence How, is beyond my understanding, the boy could fall into the ditch :- How the boy could fall into the ditch is beyond my understanding
Hence ,option A will be required answer .