Though it was the first time that I the small town I fell in love with it at once.A. was

问题补充：

Though it was the first time that I the small town, I fell in love with it at once.

A. was visiting

B. visit

C. have visited

D. had visited

答案：

A. was visiting

B. visit

C. have visited

(答案→)D. had visited

解析：句意:尽管这是我第一次参观这个小镇,但是我马上就爱上了它。it was 次数+ that +had done sth. （表示过去时）it is 次数+ that +have done sth.（表示现在时）“这是第几次做某事”。故选D。