单选题
Many thousands of hydrocarbon compounds are possible because______.
A、
the petroleum products vary greatly in physical appearance
B、
complicated refining processes rearrange the chemical structure
C、
the two atoms in the molecule assume many positions
D、
the pressure needed to force it to the surface causes molecular transformation
【正确答案】
C
【答案解析】
[解析]由第三段最后一句中“．．．which are possible because of the various positions and joinings．．．”可知选项C正确。
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