3. Please find some appropriate examples to support the topic sentence.topic sentence: Living in the city is challenging in many ways.
选项：

A:City dwellers usually pay a lot of money to live in a small apartment.;
B:People who live in the city have to deal with pollution.;
C: It is difficult to live in a city because of the busy lifestyle in cities.;
D:it is difficult to live in a city because of the comfortable life in rural area.