Examples of topic sentences. Here are examples of topic sentences with a main idea listed to help you see how the topic sentence supports the main point of a piece of writing: Example 1: Main idea: President James Polk expanded the physical land of the United States during his presidency. The following topic sentences have controlling ideas. Click on the underlined segment of the topic sentence that contains the controlling idea. Tennis racquets have changed greatly in the last ten years. People from many different cultures live in Boston. Cats are better pets than dogs for many reasons. Yesterday was the worst day of my life. Every topic sentence has two parts: a topic (what the paragraph is about) and a controlling idea (the direction the paragraph will take). Take a look at these topic sentence examples in which the topic is bold and the controlling idea is in italics. Controlling statement examples like, "Colorado has the most beautiful mountains" is an opinion. Someone may think that Montana or Tennessee has more beautiful mountains. Asking "how do you know?" can help identify the controlling idea of an opinion-based topic sentence. Identifying lists requires a "What are…" question. Step 1: Write a thesis statement The first step to developing your topic sentences is to make sure you have a strong thesis statement. The thesis statement sums up the purpose and argument of the whole paper. Thesis statement example Step 1. Decide on a controlling idea and create a topic sentence. Paragraph development begins with the formulation of the controlling idea. This idea directs the paragraph's development. Often, the controlling idea of a paragraph will appear in the form of a topic sentence. For example, one of the most common patterns in academic writing is outlined below. Topic sentence. A topic sentence introduces the main point of the paragraph. It should contain a main idea and a controlling idea which support the thesis statement and unify the content of the paragraph. For this activity, do the following: Select the word or phrase that reveals the controlling idea of the paragraph. This controlling idea will be part of the topic sentence. Click on the Show Solutions link to check your answers. Example 1. r4m8.