could:can的过去式;能,可以;能,可能;能
I could hear bells tinkling in the distance.
would:will的过去式;愿,要;常常;大概;将要,会
He foresaw that the job would take a long time.
should:将;万一,竟然;应当,应该;就,该;可能,也许;竟会;应当,该
English should be learnt Bit by Bit.
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