In some snails, protection is enhanced by a proteinaceous covering called-?

Question

1) Torson
2) Nelson
3) Halter
4) Operculum

Answer 1

Operculum is closest to correct, of the answers given, but actually the correct answer to this question is periostracum. Periostracum is the proteinaceous, fibrous covering that many snails produce over their whole shell. The operculum just plugs the aperture when the snail withdraws, so there is no reason to refer to it as a "covering".

Answer 2

4 operculum

Answer 3

Only #4 sounds familiar from reading about snails.