单选题 Grinols is primarily concerned with ______ in his new book.

A、 demonstrating the prevalence of gambling
B、 examining the benefits and costs of gambling
C、 exploring the causes of gambling
D、 showing whether the benefits of gambling outweigh its costs

【正确答案】 D

【答案解析】本题为细节理解题。据第5段可确定。