Question

8. Choose the correct form of the verbs to be and to have in the following sentence:

Answer 1

The answer is B. If we input the answer into the sentence it makes the most sense and it is more consistent in verb tense then the others. 
"Hassan is most productive when he has several hours at a time to focus on his work"<span />

Answer 2

Hi 

The correct answer is C. is......has (3rd person singular BE and HAVE)

Hassan is most productive when he has several hours at a time to focus on his work.

Hope this helps :)