As you know, a good paragraph has three parts: a topic sentence. supporting sentences. and a concluding sentence. But a good paragraph also has unity. Unity means that all of the supporting sentences are about the controlling idea in the topic sentence. Think about the model paragraph above. Topic sentence: My sister Liz was born lucky(Controlling idea) Main supporting sentences: she has a beautiful smile 2. She eats a lot and does not get fat. 3. She does not study hard but always gets good grades