英文高手請來 AR!!!!

Basically some of the words have the same meaning, for example:

must = have to
should = ought to
can = could
may = might

In a simple way, there is a tense form of the words MUST, SHOULD, CAN and MAY.

Past tense of MUST is HAVE TO
Past tense of SHOULD is OUGHT TO
Past tense of CAN is COULD
Past tense of MAY is MIGHT

The words HAVE TO, OUGHT TO, COULD and MIGHT are also used in
indirect speech, which represent the words MUST, SHOULD, CAN and MAY respectively.

Another example is WILL, when using in past tense or indirect speech, you should use WOULD.

Hope this helps.

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