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题库 / Prep2008E1-SC-246
Scientists have identified an asteroid, 2000 BF19, that is about half a mile wide and, if it strikes Earth, it can do tremendous damage to part of the planet but probably not cause planetwide destruction.
and, if it strikes Earth, it can do tremendous damage to part of the planet but
and, if it would strike Earth, part of the planet could experience a tremendous amount of damage but it would
and that, if it were to strike Earth, could do tremendous damage to part of the planet but would
and that, if Earth is struck by it, can do part of the planet tremendous damage, but it would
and that, if it strikes Earth, it could experience a tremendous amount of damage but
题目分析：
本题涉及许多虚拟语气的相关概念。
选项分析：
A选项：由于并列连词and身后没有that，且 it can do tremendous damage to part of the planet是完整的不缺少任何成分的完整句（定语从句中必然缺少某个成分），所以本选项中具有并列关系的是Scientists have identified an asteroid, 2000 BF19和 it can do tremendous damage to part of the planet。在逻辑上，前者是表述发现行星的，后者是描述行星特点的，两者没有并列关系。
B选项：本选项错误同选项(A)。另外，虚拟语气中的if从句不能用would。
C选项：Correct. 本选项在语法和逻辑上均是正确的。
D选项：并列连词but身后的it would probably not cause planetwide destruction中是完整的句子，无法和定语从句并列，只能和主句Scientists have identified an asteroid, 2000 BF19并列。同(A)理，这种并列是不成立的。
E选项：并列连词and身后的it can do tremendous damage to part of the planet是完整的不缺少任何成分的完整句，并列关系错误同选项(A)。另外，if从句用一般现在时，主句需用将来时，不能用could。
AB选项，and后面clause是完整句子，与"Scientists have identified an asteroid"平行，逻辑上不同
E选项，that后面不缺句子成分，但and that要与前面的定语从句平行，所以that也应该是引导定语从句，结构上有问题
D选项，but后面clause是完整句子，与"Scientists have identified an asteroid"平行，逻辑上不同
综上，算C选项
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