Could/should/can/might/may/would do 一般是虚拟,即有情态动词时，要注意虚拟语气。注意了解一个句子要注意时态，语态与语气
that English is difficult is not my idea.
whether he will come to my party is very important.
why dinosaurs became extinct is still a mystery.
Virginia Woolf’s provocative statement about her intentions in writing Mrs. Dalloway has regularly been ignored by the critics，since it highlights an aspect of her literary interests very different from the traditional picture of the "poetic" novelist concerned with examining states of reverie and vision and with following the intricate pathways of individual consciousness.
Gutman argues convincingly that the stability of the Black family encouraged the transmission of-and so was crucial in sustaining-the Black heritage of folklore，music，and religious expression from one generation to another，a heritage that slaves were continually fashioning out of their African and American experiences.
who is it?
i hope (that) i can visit my teacher.
i hope to visit my teacher.
my idea is that she should be sent to school.
his question is whether people will live on the moon.
he has a question whether people will live on the moon.
he has a question that everyone encounters.
his question is when people will live on the moon.
Shanghai is a place where many people choose to find opportunies.
Shanghai is where many people choose to find opportunies.
put it where it belongs.
many people choose to find opportunies where economy enjoys high proseperity.