单选题：The walls are made of hollow concrete blocks.

题目内容：

The walls are made of hollow concrete blocks. A．big
B．long
C．new
D．empty

参考答案：

答案解析：

What does the word precursor in the context in the second pa

What does the word precursor in the context in the second paragraph mean?A．A man

分类：综合类题型：单选题

The United States was the country where__________.A．in the development of air tr

分类：综合类题型：单选题

请在17处填上正确答案。A．distinguished B．different C．protected D．isolated

分类：综合类题型：单选题

请在4处填上正确答案。A．essential B．available C．reliable D．responsible

分类：综合类题型：单选题

Every day there are over（　　）high school strdents who will become regular smoker.

分类：综合类题型：单选题