题目选项分析

Nobody knows exactly how many languages there are in the world, partly because of the difficulty of distinguishing between a language and the sub-languages or dialects within it, but those who have tried to count typically have found about five thousand.

Nobody knows exactly how many languages there are in the world, partly because of the difficulty of distinguishing between a language or the sub-languages or dialects within them, but those who tried to count them typically found about five thousand.