There are a lot of in Lijiang,an ancient town in Yunnan Province

应该选D.
首先由a lot of+可数名词复数 知 可以排除A.
然后，B是旅游，C是旅游业，均不符题意.
所以选A(丽江有很多旅游者)

There are a lot of (tourists) in Lijiang,an ancient town in Yunnan Province.

云南古镇丽江有很多旅游者。