Answer: D
Explanation: Charley and Nicholas saw Porpoise in the water before he swam away. Porpoise being a great swimmer, and Charley realizing before hand that Porpoise might swim for the beach had it watched by a couple of constables. That was how Porpoise was apprehended. Therefore option D is correct because Charley realized that he may swim for the beach and had it patrolled as stated in the excerpt "....When you see a thing, you've got to see it all around, or what's the good of seeing it at all? I saw the beach, so I left a couple of constables behind to keep an eye on it. That's all."