A mollusk with one shell and a muscular foot.

A mollusk with one shell and a muscular foot.

• A. Gastropod
• B. Tentacle
• C. Bivalve
• D. Cephalopod

Answer: (C)

The question tests how mollusks are classified by shell number and how they move. A mollusk with a single shell and a broad muscular foot is characteristic of gastropods. This group includes snails and limpets; their single shell is the defining shell arrangement, and the muscular foot provides the common creeping locomotion you see when they move slowly across surfaces. Bivalves, in contrast, have two shells hinged together, which distinguishes them from a single-shell mollusk, and they use their foot mostly for digging or anchoring rather than for walking. Cephalopods typically lack an external shell or have only an internal remnant, and they rely on jet propulsion and other means of movement rather than a single, broad crawling foot. A tentacle is not a classification of mollusks but a body part found in some cephalopods. So, the description of one shell plus a muscular, creeping foot matches gastropods best.

The question tests how mollusks are classified by shell number and how they move. A mollusk with a single shell and a broad muscular foot is characteristic of gastropods. This group includes snails and limpets; their single shell is the defining shell arrangement, and the muscular foot provides the common creeping locomotion you see when they move slowly across surfaces.

Bivalves, in contrast, have two shells hinged together, which distinguishes them from a single-shell mollusk, and they use their foot mostly for digging or anchoring rather than for walking. Cephalopods typically lack an external shell or have only an internal remnant, and they rely on jet propulsion and other means of movement rather than a single, broad crawling foot. A tentacle is not a classification of mollusks but a body part found in some cephalopods.

So, the description of one shell plus a muscular, creeping foot matches gastropods best.