Select the most appropriate option to fill in the blank.
This is the ___________ book that I have read till now.

Correct option is C

The correct option to fill in the blank is (c) most interesting.
Explanation: The sentence uses the superlative form as it is comparing one book to all others read so far. The superlative form of "interesting" is "most interesting." (Hindi meaning: सबसे दिलचस्प)
Example: This is the most interesting documentary I’ve ever watched.
Explain why other options are incorrect:
· (a) interesting: Positive degree, does not show comparison (Hindi: दिलचस्प)
· (b) more interesting: Comparative, used to compare two items, not suitable here (Hindi: अधिक दिलचस्प)
· (d) better interest: Grammatically incorrect phrase