不定式作主语
To nish this report took
him a week.
注意①:主谓一致
To master a foreign
language ____ not easy.
To know what is good and
to do what is right _____
two dierent things.
注意②:形式主语
▲ It is + adj. / n. + to do.
It is not easy to master a
foreign language.
i
s
are
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