Step 1: Understanding o-acetylsalicylic acid.
O-acetylsalicylic acid is a chemical compound commonly known as aspirin, which is used as a pain reliever and anti-inflammatory agent.
Step 2: Analyzing the options.
(A) Aspirin: Aspirin is the correct answer. It is the common name for o-acetylsalicylic acid.
(B) Equanil: Equanil is a tranquilizer, not aspirin.
(C) Veronal: Veronal is a sedative, not aspirin.
(D) Valium: Valium is an anti-anxiety medication, not aspirin.
Step 3: Conclusion.
The correct answer is (A) Aspirin, which is o-acetylsalicylic acid.