1 This is the biggest lab____we have ever built in our unive

1 This is the biggest lab____we have ever built in our university.
A which
B what
C that
D where
2 Is oxygen the only gas____helps fire burn?
A that
B /
C which
D what
3 Air,____we breathe every day,is around us all the time.
A that
B /
C which
D it
4 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
5 we often think of the days____we spent together on the island.
A when
B which
C in which
D during which
6 Have you ever been to Shanghai,____I left ten years ago?
A where
B which
C that
D when
7 He has left Beijing,____a meeting is to be held.
A when
B where
C as
D which
8 This is the very place____I'm wishing to live in.
A where
B which
C that
D in which
9 Can you solve such problems____raised by the audience?
A what were
B as were
C that were
C which were
10 The reason____he didn't come was____he was injured.
A that,because
B why,that
C why,because
D that,that
11 He must be frome Africa,____can be seen from his skin.
A that
B as
C it
D what
12 His father died last year,____made it impossible for him to go abroad.
A when
B which
C as
D that
13____is natural,he married Mary.
A it
B what
C which
D As
14 All____is needed is a supply of oil.
A the thing
B that
C what
D which
15 He paid the boy 10 dollars for washing ten windows,most of____had not been cleaned for years.
A these
B those
C that
D which
16 she heard a terrible noise,____brought her heart into her mouth.
A it
B which
C this
D that
17 In the dark street,there wasn't a single person____she could turn for help.
A that
B who
C from whom
D to whom
18 The last river____they crossed is two miles wide.
A where
B which
C that
D in which