1.All this leads to a population in the twenty-first century that is smaller_____years ago.
A.than was B.that was C.than that D.it was
(为什么选A)
2.I hope that the little____I've been able to do has been of some use.
A.which B.what C.whose D.that
（为什么选D）
3.The pilot lost contact with the military base,_____the plane crashed in the desert.
A.by means of which B.for which
C,because of that D.as a result of which
(为什么选D)
4._____,television has played an important role in modern life.
A.as long as it is known B.what is known to all
C.since it is known D.as is known to all
（为什么选D）
5.Such electronic devices_____we use in a radio set are also found in a TV set.
A.that B.as C.which D.such as
（为什么选B）
6.The process_____energy is changed from one form into another is called the transformation of energy.
A.by which B.at which C.on which D.for which
（为什么选A）
7.He studied hard and later become a well－known writer,____his father had expected.
A.that was what B.it is what
C.thich was what D.and which was
（为什么选C）
8.Despite its wide range of styles and instrumentation,country music has certain connom features_____its own special character.
A.give it that B.that give it C.give that D.that gives it to
（为什么选B）
9.Edward is the boy____I think scored the winning points for the basketball team.
A.whom B.which C.that D.who
（为什么选D，whom不是可以做宾语嘛？）
1.All this leads to a population in the twenty-first century that is smaller_____years ago.
A.than was B.that was C.than that D.it was
(为什么选A)我真说不清楚
2.I hope that the little____I've been able to do has been of some use.
A.which B.what C.whose D.that
（为什么选D）little在这里是不定代词。后面的定语从句关代用that
3.The pilot lost contact with the military base,_____the plane crashed in the desert.
A.by means of which B.for which
C,because of that D.as a result of which
(为什么选D)由于那样的结果，属于介词加关代的定语从句。for 是表示原因，而句子是叙述结果的
4._____,television has played an important role in modern life.
A.as long as it is known B.what is known to all
C.since it is known D.as is known to all
（为什么选D）as引导非限定性的定语从句，可以放到句首
5.Such electronic devices_____we use in a radio set are also found in a TV set.
A.that B.as C.which D.such as，
（为什么选B）先行词被such修饰关代用as
6.The process_____energy is changed from one form into another is called the transformation of energy.
A.by which B.at which C.on which D.for which
（为什么选A）介词by是通过的意思。也是介词加关系代词引导的定语从句
7.He studied hard and later become a well－known writer,____his father had expected.
A.that was what B.it is what
C.thich was what D.and which was
（为什么选C）which引导了一个非限制性的定语从句，从句里有what 引导的表语从句
8.Despite its wide range of styles and instrumentation,country music has certain connom features_____its own special character.
A.give it that B.that give it C.give that D.that gives it to
（为什么选B）that引导定语从句that代替先行词feature
9.Edward is the boy____I think scored the winning points for the basketball team.
A.whom B.which C.that D.who
（为什么选D，whom不是可以做宾语嘛？）i think 作插入语，，定语从句缺少主语