an

Which is ________,an elephant or a tiger?

I do not intend to follow that, because we shall have an opportunity to do so on another ______.

Mary never turned _____at the cinema, although I waited over an hour.

The Web also provides an environment in which it is quick and easy to ______ ideas with colleagues.

It turned out that the man was an excellent policeman working in New York , _____ had contributed a lot to the case.

----We __________ an English exam. I’m not good at English. What should I do?----You can ask your teacher for help

I was worried about my maths, but Mr. Brown gave me an A.          .

以1949年a0为最初水平，1997年an为最末水平，计算钢铁产量的年平均发展速度时，应当开48次方。（）