請(qǐng)英語(yǔ)高手解答有幾個(gè)語(yǔ)法題
改錯(cuò)（我想知道的是為什么那么改）
1.A large number of land has been covered by deserts.（答案是把number改為amount）
2.1.A large number of land has been covered by deserts.（答案是把number改為amount）.（答案是second前面加a）
3.She is the second to none in her studies.（答案是去掉the）
我想知道選擇的選項(xiàng)選它的原因是什么
4.We always keep _______spare paper,in case we ran out.
A.too much B.a number of C.plenty of D.a good many
5.He did it _it took me.
A.one-third a time B.one -third time C.the one-third time D.one-third the time
6.It is reported that the US uses_________energy as the whole of Europe.
A.as twice B.twice much C.twice as much D.twice much as
7The house you bought is_____mine.
A.as three times as B.three times the size of C.three times the size than D.as big as three times than