Answer and Explanation:
You should use multiple sources to show that your essay has a diversity of information, being a rich essay, where you researched different points of view and endeavored to create it according to several relevant works on the subject. In addition, multiple sources provide more support for you to create your arguments and your own original ideas, as it offers you a more complete range of information.
Answer:
The answer is
Schools can use written materials about television to explore its place in today’s culture and to teach reading, writing, and thinking skills.
Explanation:
Its usually written as the first sentence of the paragraph (although its not necessary but preferred) It basically includes the main idea or the topic of the paragraph (doesn't have to be word for word), and states the main points of the paragraph briefly.