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

will have stayed

注意arrive的一般時態表示將來的動作。

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)和不定式連用，可以表示多種意思，并常用于條件從句(如果想要……)。

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

was being repaired

while+主語+謂語(一般過去時或過去進行時)表示過去某段時間內主語的狀態或正在進行的動作，所以主句謂語應用過去進行時。

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的句型中常用現在完成時。

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“近來”recently。