1)、By the time you arrive in London,we_____(stay)in Europe for two weeks.

will have stayed

注意arrive的一般时态表示将来的动作。

2)、The first two factors must be equal for all who are being compared,if any comparison in terms of intelligence____(make)

is to be made

be（am/is/are;was/were)和不定式连用，可以表示多种意思，并常用于条件从句（如果想要......）。

3)、While you were in London that year,the London Bridge_____(repair).

was being repaired

while+主语+谓语（一般过去时或过去进行时）表示过去某段时间内主语的状态或正在进行的动作，所以主句谓语应用过去进行时。

4)、John is't a diligent student,for it is the third time he____(be)late,isn't it?

have been

在it is the third time的句型中常用现在完成时。

5)、John always works in his lab and makes a lot of experiments,He___(make)experiments all afternoon and____(not finish)yet.

have been making

have not finished

6)、It___(be)very cold lately,but it's beginning to get a bit warmer.

has been

注意lately，表示"近来"recently。