44. It was during his stay in the countryside ______ he began to learn English.
A. when
B. that
C. which
D. what

解析：
该题考查的是it is / was ... that ...强调句型。
该句强调的是it was和that之间的部分“during his stay in the countryside”，该部分在剧中作的是状语。
如不强调，可还原为：He began to learn English during his stay in the countryside.
参考译文：
在乡下待的那段时间里，他开始学习英语。
其他语言点：
stay：n. / v. 停留
begin to do：开始做……