______ with the size of the whole earth, the highest mountains do not seem high at all.A. If you compare B. Compare them C. When compared D. A comparison 为什么选C其他选项错在哪里

______ with the size of the whole earth, the highest mountains do not seem high at all.A. If you compare B. Compare them C. When compared D. A comparison 为什么选C其他选项错在哪里
______ with the size of the whole earth, the highest mountains do not seem high at all.
A. If you compare 
B. Compare them
C. When compared 
D. A comparison
为什么选C其他选项错在哪里

______ with the size of the whole earth, the highest mountains do not seem high at all.A. If you compare B. Compare them C. When compared D. A comparison 为什么选C其他选项错在哪里
A.错在前后主语不一致,前面说you,后面说mountain
B.Compare 是动词原形,没有主语
D.A comparison 是名词,可以用来作主语,但是前半句又没有谓语了

主句的主语是the highest mountains ，选项When compared是时间状语从句省掉了they are .
A选项中如果加上  If you compare （them)就对了。B选项的话，就是两个独立的句子，但是没有连接词。D选项无法构成从句。

A. 错在前后主语不一致，前面说you，后面说mountain
B. Compare 是动词原形，没有主语
D. A comparison 是名词，可以用来作主语，但是前半句又没有谓语了

copare A with B 用B和A比较
A项目，缺少比较对象A
B项目，应为comparing 分词作状语
D没有这种用法，compare with，compare是动词

好好学习