Answer:
D. sentence 3, because it grabs the reader's attention with a startling statistic.
Step-by-step explanation:
This is the sentence that would best be used as an introduction to this text. When we write the opening sentence of a paragraph, we often want to use a "hook." A hook is a statement that is attractive or interesting and convinces the reader to continue reading. In this case, the interesting fact is the statistic. This statistic grabs the reader's attention, and thus is best employed at the beginning of the paragraph.