This book is a useful …… to our library. A. discovery B. asset C. addition D. arrival

The correct answer is C. addition.

A discovery is something that is found or learned for the first time. An asset is something that is valuable or useful. An addition is something that is added to something else. An arrival is the act of coming to a place.

In this case, the book is a useful addition to the library because it provides valuable information that can be used by library patrons.