The correct answer is option 1, William H. McNeill. In this question, we are asked to identify the author of the book `Plagues and Parks`. Let`s analyze each option to understand why option 1 is the correct answer.

Option 1: William H. McNeill - This author is known for his book `Plagues and Parks`, which explores the impact of diseases and urban planning on human history. Since the book title matches the question, it is a strong possibility that William H. McNeill is the correct author.

Option 2: WI. Thomas - This author`s name does not match the book title, so it is unlikely to be the correct answer.

Option 3: Rachel Carson - Although Rachel Carson was a renowned author and environmentalist, `Plagues and Parks` is not a book associated with her. Therefore, option 3 is not the correct answer.

Option 4: David Cannadine - Similar to the previous options, David Cannadine is not known for writing `Plagues and Parks`. Hence, option 4 is not the correct answer.

In summary, among the given options, the author of the book `Plagues and Parks` is William H. McNeill.