NP ⊆ MA

Inclusion · folklore

Statement

$\mathbf{NP}\subseteq \mathbf{MA}$: every language in NP has a Merlin–Arthur proof system with perfect completeness and perfect soundness — folklore.

Sketch

Merlin sends an $\mathbf{NP}$ witness and Arthur, ignoring his coins, checks it with the deterministic $\mathbf{NP}$ verifier, so completeness and soundness are those of that verifier.