The following are multiple choice questions (with answers) about medical knowledge.   **Question:** Methacholine acts at which receptor?   (A) M1   (B) M2   (C) M3   (D) M4
['(B) M2 <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) M1 \n (B) M2 \n (C) M3 \n (D) M4 <> possible answers', '  Methacholine acts at which receptor? <> context@']