Read the following paragraph and underline the topic sentences.
English has almost become an international language. Except for Chinese, more people speak it than any other language. Spanish is the official language of more countries in the world, but most countries have English as their official or unofficial second language. More than seventy percent of the world's mail is written in English. In international business, English is used more than any other language, and it is the language of airline pilot and air traffic controllers all over the world. Moreover, although French used to be the language of diplomacy, English has displaced it throughout the world. Therefore, unless you plan to spend your life alone on a desert island in the middle of the Pacific Ocean, it is a useful language to know.