1 . （2015·安徽）         scientists have learned a lot about the universe, there is much we still don’t know.

A．Once	B．Since
C．Though	D．Unless

2 . The meaning of the word “nice” changed a few times ________ it finally came to include the sense “pleasant.”

A．before	B．after
C．since	D．while

3 . The exact year _____ Angela and her family spent together in China was 2008．

A．When

B．where

C．why

D．which

4 . Walmart, which is one of the largest American supermarket chains,        some of its stores open 24 hours on Mondays through Saturdays.

A．keeps	B．keep
C．have kept	D．had kept

5 . A lot of language learning, ________has been discovered, is happening in the first year of life, so parents should talk much to their children during that period.

A．what	B．that
C．where	D．as

6 . Mo Yan was awarded the Nobel Prize for Literature in 2012, ________ made one of the Chinese people’s long-held dreams come true.

A．it	B．that
C．what	D．which

7 . It's much easier to make friends ________ you have similar interests.

A．unless	B．when
C．even though	D．so that

8 . From space, the earth looks blue.This is _______about seventy-one percent of its surface is covered by water.

A．why	B．how
C．because	D．whether

9 . The field research will take Joan and Paul about five months；it will be a long time________we meet them again.

A．after	B．before
C．since	D．when

10 . You can only be sure of _____ you have at present; you cannot be sure of something _____ you might get in the future.

A．that; what

B．what; /

C．which; that

D．/; that