河流由窄变宽的地方是冲积砂矿床形成的有利地段。()
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矿石构造系指矿石中矿物集合体的特点，包括集合体的形状、大小以及集合体之间的相互关系。()
The word "intractable"(line 4, para. 1)most likely means "______".
A. disturbing
B. unfavorable
C. infuriating
D. insoluble
According to the text, people are curious about sources of creativity because______.
A. creativity is profitable
B. creativity is a basic human instinct
C. creativity is directly related to diversity
D. creative thought is valued by almost everybody
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