问题描述：
Most scientists now think that the moon was once part of Earth.
为什么这里的part前面没有加a?
trains travelling to different parts of a city mean fewer cars and buses on our roads.
为什么mean不加s?不是应该动名词做主语用三单一的么?
解释下、谢、
为什么这里的part前面没有加a?
trains travelling to different parts of a city mean fewer cars and buses on our roads.
为什么mean不加s?不是应该动名词做主语用三单一的么?
解释下、谢、
问题解答：
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