11. All the apples ______ fell down from the tree were eaten up by the pigs.
A. which
B. /
C. that
D. they
12. I can tell you ______ he told me last week.
A. all which
B. all what
C. that all
D. all that
13. This is the biggest lab ______ we have ever built in our university.
A. which
B. what
C. that
D. where
14. Is oxygen the only gas ______ helps fire burn?
A. that
B. /
C. which
D. what
15. Air, ______ we breathe every day, is around us all the time.
A. that
B. /
C. which
D. it
16. This is the museum ______ we saw an exhibition the other day.
A. that
B. which
C. where
D. in that
17. This museum is ______ you visited the other day.
A. that
B. which
C. where
D. the one
18. This is the museum ______ you saw the other day.
A. that
B. where
C. in which
D. in that
19. It is the third time ______ late this month.
A. that you arrived
B. when you arrived
C. that you've arrived
D. when you've arrived
20. It was in 1969 ______ the American astronaut succeeded in landing on the moon.
A. that
B. which
C. in which
D. when
