Tom is believed _____ handsome when he was in college.

1.答案：B.
2.
1）此题考查believe的固定结构.
believe sb/sth (to be) + 名词/形容词 “认为某人/物是...”
2) 但是如果“to be (to be) + 名词/形容词”所表示的事实发生在believe之前的话,则改用：believe sb/sth to have done sth.
此时,to have done sth中的to have done是不能省略的.
3）此题刚好指的是“在读大学”的时候,早就发生了,所以用believe sb/sth to have been handsome.
4）上述结构如果改成被动语态即：sb/sth be believed to have done sth
3.综上所述,答案为B.

A. to be 过去曾是

A,这是sb is believed to behave done sth 的句型，而句末有when he was in college，所以是表示过去的时间，不能用现在完成时。