—Did you receive the letter the next day?—No. Somehow it was three weeks I received it.A

问题补充：

—Did you receive the letter the next day?

—No. Somehow, it was three weeks I received it.

A. since

B. before

C. that

D. when

答案：

A. since

(答案→)B. before

C. that

D. when

解析：考察特殊句式。固定句式：It be 一段时间 before…一段时间以后某事才发生；如果before后面使用一般现在时，前面的主语使用将来时；如果before后面使用一般过去时，前面也使用一般过去时；句义：—你第二天收到那封信了吗？—没有。不知道为什么，我三个星期以后才收到。故B正确。