The play begins at 6: 40 pm. So we have to be at the theatre 6:30 pm at the latest. A. af

问题补充：

The play begins at 6: 40 pm. So we have to be at the theatre 6:30 pm at the latest.

A. after

B. around

C. until

D. by

答案：

A. after

B. around

C. until

(答案→)D. by

解析：从“戏剧在下午6:40开始”可知到达剧院的时间最迟不应晚于6:30。A项表示“下午6:30后到剧院”，C项表示“在剧院呆到下午6:30为止”，均不合题意。B项干扰性最强，around意为“左右，大约”, 但在6:30 pm后有at the latest“最晚”,二者相矛盾。C项by是not later than(不迟于)之意，整合题意。