以下15题,麻烦给下答案,顺便简单地解释下为什么这么选.

以下15题,麻烦给下答案,顺便简单地解释下为什么这么选.
1.We agreed to accept( ) they thought was the best manager
A.whatever B.whoever C.whichever D.whoever
2.Ten men banded together in love can do( ) ten thousand separately would fail in.
A.where B.what C.which D.that
3.The latest UK official studies show( )fewer teenagers are now studying foreign languages.
A.what B.which C.不填 D.whether
4.What doctors really doubt is( )my mother will recover from this serious disease soon or not.
A.when B.how C.whether D.if
5.With the eyes fixed upon( )was left of Della's hair,jim was wearing quite a strange expression.
A.what B.all C.which D.that
6.Zheng He's first stop was in( )is today of Vietnam.
A.where B.which C.that D.what
7.Being determined is a king of quality and that's ( )it takes to do anything properly.
A.how B.which C.where D.what
8.Try recording your voice in English---this may help you to see( )you could improve.
A.that B.where C.how D.when
9.I want to make ( )clear that we should do an important and necessary job.
A.that B.this C.it D.what
10.The last time we saw Miss Smith was ( )we visittd her home.
A.when B.how C.where D.why
11.I still don't remember( )I crossed the street with the red light still on.
A.when it was that B.that is was when C.where was it that D.it was where that.
12.One reason I know ( ) business is a challenge is ( )best guesses must be well prepared in terms of incomplete information.
A.which；because B.不填；because C.that;why D.why;that
13.Only when enough attention( )to the environment ( )it will be improved greatly.
A.pays;one can expect B.is paid;can one expect C.paying;can one expect D.to be paid;one is to expect
14 When we came in ,we were surprised to find Carl,the bravest boy in our class,( )at the back of the classroom.
A.weeps B.to weep C.weeping D.wept
15.Gary was such an honest boy ( )we all believed ( )he spoke the truth to us.
A.不填；whatever B.that;what C.不填; that D.that;不填