You should (1)/ be always greatful (2)/ to your mentor. (3)/ No error (4)

Options

A. 1 You should
B. 2 be always greatful
C. 3 to your mentor.
D. 4 No error

Answer

2

Explanation

grateful will replace greatful because - there is no such word as greatful
grateful (Adj.): thankful as in
I.m grateful for your help.
mentor (Noun) means a teacher.