有几个英语时态的选择搞不懂,

题目

有几个英语时态的选择搞不懂,
1.An unexpected heavy rain caused severe flooding,and the water_____all the time.
A.rose B.raised C.was rising D.was raising
（为什么选D不能选C）
2.--What are you doing under the table?
--I____to find my watch.
A.tried B.try C.am trying D.have tried
(为什么选D不能选C)
3.I will ask her for the book now,for she_____plenty of time to read since I lent it to her.
A.has B.has had C.had had D.was having
(为什么选B不能选C）
4.We are late.I expect the film will already have started by the time we get to the cinema.
A.will already have started
B.would already have started
C.shall have already started
D.has already been started
（为什么选A不选B)

答案

第一个：考的是rise和raise的区别、时态.你第一个不懂,不是因为你不懂时态,而是你不懂它们的区别.
第二个：我认为答案是C,因为按照语境,对方是问你“你正在桌下干什么”,无疑是问你现在在做什么.
第三个：since是“自···以来”,是典型的完成时态标志.而后面的lent是过去时,我将向她要回来,是过去到现在,就是选B
第四个：这个是因为句中有“get”而不是"got",前者是现在时,后者是过去时,因此选A.