单选题：Sedimentary rocks cover much of the Earth's surface, but the

题目内容：

Sedimentary rocks cover much of the Earth's surface, but they are often hidden by a thinveneer of soil. A．concealed
B．eroded
C．protected
D．softened

参考答案：

答案解析：

Because of harsh weather conditions, more than a dozen state

Because of harsh weather conditions, more than a dozen states in the United Stat

分类：理工类题型：单选题

At first glance, a forest appears to be a haphazard collection of trees, shrubs,

分类：理工类题型：单选题

Organic chemistry helps to produce materials that are________A．as good as wool B

分类：理工类题型：单选题

Rock climbing is hazardous.A．interesting B．dangerous C．attractive D．useful

分类：理工类题型：单选题

分类：理工类题型：单选题