44. It was during his stay in the countryside ______ he began to learn English.
A. when

B. that

C. which

D. what

原题解析：本题考查强调句用法。当强调的部分为状语时，只能用that，本句强调部分为 during his stay in the countryside ，为时间状语，因此正确选项为B。
参考译文：在农村的那段时间，他开始学英语。