16.___________ being used in industry,laser can be applied t

16.___________ being used in industry,laser can be applied to operations in the hospital.
选项:
a、Except for
b、In addition to
c、 Out of
d、 In spite of
17._________ on a clear day,far from the city crowds,the mountains give him a sense of infinite peace
选项:
a、If walking
b、Walking
c、 While walking
d、 When one is walking
18.The Vikings are believed ___________ America.
选项:
a、to have discovered
b、to discover
c、in discovering
d、 to have been discovered
19.Husband and wife with a common duty to the country will find themselves __________closer together.
选项:
a、drawn
b、drawing
c、 to draw
d、been drawn
20.Prisons in some countries are short of staff,___________ means each prison officer is overworked and underpaid.
选项:
a、which
b、this
c、what
d、 it
21._________ you return those books to the library immediately you will have to pay a fine.
选项:
a、Until
b、 If
c、 Unless
d、 Provided
22.So little _________ about maths that the lecture was completely beyond me.
选项:
a、I konw
b、 I knew
c、do I know
d、did I know
23.__________ the 1500s ____________ the first European explored the coast of California.
选项:
a、It was not until/ then
b、 It is not until/ when
c、 It is until/ that
d、It was not until/ that
24.Here we found little snow,as most of it seemed _________ blown off the mountain.
选项:
a、to have been
b、to be
c、that it had been
d、that it was
25.Choose the best topic sentence from the group below.
选项:
a、More and more students have part-jobs out of campus.
b、 The population of university students having part-time jobs is increasing quickly.
c、Part-time jobs can foster university students' sense of competition.
d、More people support students to have part-time jobs.

16 b 17d 18.a 19.a 20 .a 21.c 22.d 23 d 24.a 25.a