How do slugs differ from snails in terms of shell presence?

• A. Slugs have a coiled external shell
• B. Slugs have a small external shell
• C. Slugs lack a prominent external shell (or have a reduced internal shell)
• D. Snails have no shell

Answer: (C)

Shell presence is the key difference between slugs and snails. Slugs have no prominent external shell, and in many species there’s only a small internal shell vestige. This gives slugs a smooth, soft body that can squeeze into tight spaces. Snails, on the other hand, carry a visible, coiled external shell on their back, which remains a defining feature of their appearance. So the best description is that slugs lack a prominent external shell (or have a reduced internal shell). The other ideas don’t fit because a coiled external shell is typical of snails, and snails do have shells, not no shell.