2012广东高考英语语法填空答案疑问

题目

2012广东高考英语语法填空答案疑问
17题为什么是would buy而不是had bought；；22题为什么是which而不是who；；24题为什么是if/whether而不是what
原文和我做的答案：
Mary will ever forget the first
time she saw him.He suddenly appeared in class one day ,__16wearing_(wear) sun glasses .He walked in as if he __17would buy（had bought?）___
(buy) the school,And the word quickly got around that he was from New York City.
For some reason he sat beside
Mary.Mary felt _____18pleased_ (please),
because there were many empty seats in the room .But she quickly realized that
it wasn’t her,it was probably the fact that she sat in __19the___last row.
_20Although__
he thought he cloud escape attention by sitting at the back,he was wrong.It
might have made it a little _____21harder____ (hard)
for everybody because it meant they had
to turn around,but that didn’t stop the kids in the class.Of course whenever
they turned to look at him,they had to look at Mary,_22which?__made her feel like a star.
“Do

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