Oral vs. Injected Vaccines for TB

Steps:

• Identify that oral vaccines target gut pathogens and survive stomach acid, like polio vaccine.
• Note TB vaccine (BCG) is injected intradermally to mimic respiratory infection in lungs.
• Recall statements likely include: 1) acid stability, 2) site-specific immunity, 3) bacterial survival.
• Determine only statement 2 explains TB's injection need due to lung targeting.

Why D is correct:

• Statement 2 ties to immunology principle: vaccines must match infection route for mucosal immunity in respiratory tract.

Why the others are wrong:

• A includes irrelevant statements 1 and 3.
• B adds incorrect statement 1 on acid stability.
• C adds incorrect statement 3 on bacterial factors.

Not enough information on exact statements, but D fits standard TB vaccine rationale.

Final answer: D