What is the protein coat of a virus called?

A) Envelope
B) Capsule
C) Capsid
D) Phage
E) Pilus

Envelope

A flat, usually rectangular or square paper container used for sending letters or documents, or the outer covering of a structure.

Pilus

A hair-like appendage found on the surface of many bacteria, involved in adhesion to surfaces and in bacterial conjugation.

Capsid

Protein coat surrounding the nucleic acid of a virus.