The given answer is D.about 30,000,000 square miles. The passage states that the Pacific Ocean covers about one-third of Earth's surface, while the Atlantic Ocean is also large but smaller than the Pacific. Since the Pacific Ocean is so big that all of the land on Earth could fit into it, it can be inferred that the area of the Pacific Ocean is significantly larger than the Atlantic Ocean. Therefore, option D, about 30,000,000 square miles, is the best answer.