问几个问题，请朋友指教一下，谢谢！

81．In 1973 mortgage payments reprensented twenty-one percent of an
anverage thirty-year-old male’s income;and forty-four percent in 1984.

A.     
income;and forty-four percent
in 1984

B.     
income;in 1984 the figure was
forty-four percent

C.     
income,and in 1984 forty-four
percent

D.    
income,forty-four percent in
1984 was the figure

E.     
income that rose to forty-four
percent in 1984

这个题不太明白的是C项为什么不可以看作是一种相同位置的省略

89．A recent national study of the public schools shows that there
are now one microcomputer for thirty-two pupils,four times as many than there
were four years ago

A.     
there are now one microcomputer
for every thirty-two pupils,four times as many than there were

B.     
there is now one microcomputer
for every thirty-two pupils,four times as many than there were

C.     
there is now one microcomputer
for every thirty-two pupils,four times as many as there were

D.    
every thirty-two pupils now
have one microcomputer,four times as many than there were

E.     
every thirty-two pupils now has
one microcomputer,four times as many as

答案是C，不明白最后那个were为什么是对的

91．Like many self-taught artists,Perle
Hessing did not begin to paint until she was well into middle age.

A.     
Like

B.     
As have

C.     
Just as with

D.    
Just like

E.     
As did

A 和D有什么区别吗？

先看看这个

http://forum.chasedream.com/dispbbs.asp?BoardID=23&ID=70082