Hi Tuan, This is an excellent question. Yes, you have identified the topic and controlling idea well. Here is another way to approach it:
Topic 1 – Problems in large cities
Controlling idea – why is it an effective solution for governments to encourage people to move to rural areas. Give two clear points (a body paragraph for each) on how this will solve the problems of big cities.
Good studies and do email me your response for a score estimate to [email protected]