Read the following text from a student essay. How can the writer best improve his or her ideas and development?
Why is smoking cigarettes bad for your health? Cigarettes contain poisonous substances like carbon monoxide and tar, which can harm every part of your body. Smoking causes heart disease and damages your blood vessels. Eating a diet high in fat, sugar, and salt can also lead to heart disease. A lack of exercise contributes to heart disease, too. Smoking damages your lungs and can cause breathing problems or lung cancer. In fact, it can cause cancer in any organ in your body.

 - by focusing on one main idea
 - by stating the main idea clearly
The writer could best improve his or her ideas and development by focusing on one main idea.
For example, the writer could remove the underlined text to focus only on the reasons why smoking cigarettes is bad for your health.
Why is smoking cigarettes bad for your health? Cigarettes contain poisonous substances like carbon monoxide and tar, which can harm every part of your body. Smoking causes heart disease and damages your blood vessels. Eating a diet high in fat, sugar, and salt can also lead to heart disease. A lack of exercise contributes to heart disease, too. Smoking damages your lungs and can cause breathing problems or lung cancer. In fact, it can cause cancer in any organ in your body.