1. This book is the ________ book ever! a. most interesting b. more interesting c. interesting d. interestingest

The correct answer is a. most interesting.

*Explanation:*
The sentence requires the superlative form of the adjective "interesting". Since "interesting" is a long adjective, we use "most" to form the superlative degree. The correct sentence is: "This book is the most interesting book ever!"

*Translation:*
Эта книга - самая интересная книга когда-либо!