His book has a short but useful introduction.

The correct answer is A. deduction.

An introduction is the

beginning of a book, article, or other piece of writing. It is typically used to introduce the topic of the work, provide background information, and state the thesis or main argument. A deduction is a logical argument in which a conclusion is drawn from a set of premises. In the context of the question, the word “deduction” is most likely being used to refer to the introduction of the book. The introduction is a short but useful part of the book that provides background information and states the thesis or main argument.

The other options are incorrect. B, end, is the opposite of introduction. C, termination, is the act of ending something. D, conclusion, is the final part of something.