急！高手帮忙，几个语法题

1.Computers that once took up entire rooms are now _____to e put on desktops ang into watches.
A as small as B small enough C smaller than D so small
2.-Sometimes students may have ____ themselves.
-Let's see what we can do to help them.
A difficulty expressing B difficulty to express C difficulties expressing D difficulties express
3.We have a big library in our school.There are more than twice___ five years ago.
A books than B as many books as C many more books than D many books as
4.I carefully poured the liquid into the water, my classmates____anxiously beside me to see what would happen.
A stood B standing C to stand D were standing
希望能帮我解释一下，最好能保证正确率，谢谢！！！

1.Computers that once took up entire rooms are now _____to e put on desktops ang into watches.
A as small as B small enough C smaller than D so small
B enough 修饰形容词要后置
as small as 不能接不定式
2.-Sometimes students may have ____ themselves.
-Let's see what we can do to help them.
A difficulty expressing B difficulty to express C difficulties expressing D difficulties express
A 固定句型 have trouble/ difficulty in doing sth
做某事有困难
3.We have a big library in our school.There are more than twice___ five years ago.
A books than B as many books as C many more books than D many books as
B as many/ much as 和。。。一样多
4.I carefully poured the liquid into the water, my classmates____anxiously beside me to see what would happen.
A stood B standing C to stand D were standing
B：独立主格结构

1. B 从前的电脑大得占据整个房间，现在的小得可以放在
桌上甚至手表里。这题打错了好几个字。
2 C 学生有时表达有困难。学生很多，困难不止一个。
3 B 新图书馆的书比五年前多了两倍都不止。
4 A 简单过去。