The correct answer is C) Manila line stoppers should not be used for holding nylon hawsers. The reason is that nylon lines and manila lines have different physical properties. Nylon is a synthetic material that is more elastic and prone to slipping compared to natural fiber manila lines. Using manila line stoppers, which are designed for the less slippery manila, would not provide a secure hold on the more slippery nylon hawsers. Instead, nylon lines should be secured using methods specifically designed for nylon, such as keeping an extra turn on the bitt as mentioned in option A. The other options are recommended practices for handling nylon lines, such as scrubbing down slippery lines (B) and thawing and draining iced-over lines (D) to maintain their integrity and safety.