Answer: A. Explain why the only upper classes could afford to drink tea
Explanation:
In the excerpt, McGregor introduces a history of tea, and mentions important historical figures - such as Queen Anne - that drank it. He later mentions Samuel Johnson, a distinguished English writer, who considered himself "a happy addict." What McGregor wanted to achieve by this is to point out that tea consumption first started in the upper class - other people could not afford it.
