急 英语语法题 请帮我选出答案 并解释一下 非常感谢

Question

1. ____in the past, at the moment it is a favorite choice for wedding gown.
A. Unpopular has as white been B. White has been as unpopular　
C. Unpopular has been as white D. Unpopular as white has been
. ____for a long time, the fields are all dried up.
A. There has been no rain B. Having no rain　　
C. There having been no rain D. There being no rain
Televisions enable us to see things happen almost at the exact moment____.
A. which they are happening B. they are happening　　
C. which they happen D. they have happened

Answer 1

1. D
as 引导的让步状语从句要倒装
2. C
这是一个独立主格结构，There having been no rain 的完整结构是There has been no rain
主语是 no rain
两个部分因为主语不同 加之是主语+非谓语形式(可带宾语）故可以判断为独立主格结构；
使用完成时是强调未下雨对田野的影响。
3. B.
at the exact moment
在此作为连词，其后可以直接加；一个完整句子they are happening　　
类似的还有 the moment / the minute / immediately等词
若去掉at 会更恰当些。
A.which they are happening 若把which改为when就是一个定语从句了。
选现在进行时的原因在于强调那个时刻的动作。
moment引导同位语从句这个说法是错误的，作为同位语从句必须是说明名词内容的，一般moment后也不加同位从，其后加同位从的名词有 information / news / ideas / suggestions etc.

Answer 2

1. D
as 引导的让步状语从句要倒装
e.g. young as he is, he knows a lot.
2. c.
考查句与句之间的关系。句与句之间要么并列要么从属。从题中看没有并列连词，所以应是从属关系。又因为存在先后关系，选c
3. b

Answer 3

1D 2C 3B

Answer 4

1. D as 引导的让步状语从句要倒装
2. C 主句是后半句，前半句当然是伴随，示为一种状态。完成时表示从过去到现在一直no rain
3. B moment引导同位语从句 the moment=they are happening