Select the most appropriate option to substitute the underlined segment in the given sentence. If no substitution is required, select No improvement. He has been solving this sum for a couple of hours and he did not solve it yet. (a) No improvement (b) has not solved it (c) has not solve it (d) had not solved it

Options

A. No improvement
B. has not solved it
C. has not solve it
D. had not solved it

Answer

B