I saw him (1)/ coming out of the hotel (2)/ on 10 o'clock. (3)/ No error. (4)

Options

A. 1 I saw him
B. 2 coming out of the hotel
C. 3 on 10 o'clock.
D. 4 No error

Answer

3

Explanation

at will replace on because -
at (Prep.) is used for pointing out specific time.
Hence, at 10 O.clock is the right usage.