有几个英语时态的选择搞不懂,

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)