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1·But it's not really the fact that the thing crosses at two places, because the line could be wiggly, the curve could be wiggly, and it could have crossed back and forth a number of times.

其实并不是因为这条线与曲线有两个交点，因为这条线可能是扭来扭去的，这条曲线可能是扭来扭去的，甚至前前后后绕来绕去好几次都有可能。