Penicillin's key properties Steps:

• Identify the statements: Assume 1 (beta-lactam antibiotic), 2 (targets bacterial cell wall), 3 (ineffective against viruses).
• Verify each: Statement 1 correct as penicillin contains beta-lactam ring inhibiting cell wall synthesis.
• Confirm statement 2: Disrupts peptidoglycan cross-linking in bacteria.
• Confirm statement 3: Antibacterial only, no antiviral activity.

Why A is correct:

• All three statements align with penicillin's mechanism as a bactericidal antibiotic per microbiology definitions.

Why the others are wrong:

• B omits 3, but penicillin is not antiviral.
• C omits 2, but cell wall inhibition is core action.
• D omits 1, but beta-lactam structure is essential.

Final answer: A