外国的朋友问“is it pretty in china and is it crowded?"我要怎么用英语回答好呢？

yes,sometimes.

yes..China is pettry..but why do you think it is crowded??
only because it has large population?

Yes China is quite crowded as compared with western countries. About pretty, are you asking about landscape or people?

Yes, China is very beautiful !Sometimes very busy, but not crowded.