中华人民共和国的英文缩写是______.

He is very clever. At age 6, she _____to play the piano.

Do you know _________?– Yes, I do. She came here on foot.

There is still a copy of this book in the library. Will you go and borrow _________? –No, I will buyin the bookstore.

How about the pollution in the countryside?—Luckily, it’s not as serious as _______ in the big cities.