【正确答案】 A

【答案解析】【解析】题意：使我疑惑的是，为什么他的书如此受欢迎。句子中puzzles的意思是使人迷惑。A中confuses的意思是使困惑；例句：They confused me by their conflicting advice.他们的建议相互矛盾，把我弄糊涂了。 　　B中shocks的意思是使人震惊；例句：We were shocked by the news of his death. 　　他去世的消息令我们震惊。 　　C中influences的意思是影响；例句：It is not his parents that influence him so much as his teachers,他的父母并不像他的老师对他那样有影响。 　　D中concerns的意思是关系到；关心；例句：The letter is chiefly concerned with export commodities.这封信主要是关于出口商品的。故选A。