I know that Bob is not much of a football player , but when ________ to maths, he is among the top three in class.
A.he refersB.it comesC.he leadsD.it concerns在线课程B
【巧解导析】四个选项中，refer to表示“谈到，提到，查询”；when it comes to为固定句式，表示“至于，谈到”；lead to表示“通向，导致”；concern表示“关心”，常用be concerned with/about结构．