It is time (1) / we should have done (2)/ something useful. (3)/ No error (4)

Options

A. 1 It is time
B. 2 we should have done
C. 3 something useful.
D. 4 No error

Answer

2

Explanation

did will replace should have done because -
we use the expression
It.s time + Subject + Past Verb form to refer to the Present moment.
It is time + we + did It is time + we + got back there.
It is time + we + found out
Hence, we did is the right usage.