问题

I think this is ______ useful book.
A:a
B:an
C:the
D:/;
B:an
C:the
D:/;
正确答案是:
同类题型
He used up late, but now he is used to up early.
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____ for London on business upon my arrival, so I didn’t see him.
Not until the early years of the 19thcentury______ what heat is.
___ student gets the first place will get a beautiful present