The topic sentence contains two parts: the topic and a controlling idea. The topic is WHAT the paragraph is going to be about, and the controlling idea explains WHY the paragraph is being written
As you see in the following example , topic is not the first part of the sentence . .
Topic Sentence: There are many reasons why pollution in ABC Town is the worst in the world.
- The topic is "pollution in ABC Town is the worst in the world" and the controlling idea is "many reasons"