Directions: Fill in the blank with an appropriate word. The question is followed by four suggested answers. Choose the most appropriate one.

He has written an ________ book on Indian history.

The correct answer is 'exhaustive' because it means comprehensive, thorough, or covering all aspects - exactly what you'd want from a book on Indian history. 'Complete' is grammatically awkward (we'd say 'a complete book' not 'an complete book'). 'Exhausting' means tiring (describing the effect on reader, not the book's scope), and 'explanatory' means explaining something.