Antibiotic Misuse Drives Resistance

Steps:

• Statement 1 fails to eradicate all bacteria, allowing resistant ones to survive and proliferate.
• Statement 2 uses subtherapeutic doses, selecting for resistant strains over time.
• Statement 3 applies antibiotics prophylactically in farming, exposing broad bacterial populations to selective pressure.
• All three statements contribute to resistance; no fourth statement exists, eliminating options with it.

Why A is correct:

• Suboptimal antibiotic exposure enables natural selection of resistant bacteria, as defined by evolutionary biology principles.

Why the others are wrong:

• B references nonexistent statement 4.
• C excludes statement 2, a key misuse factor.
• D references nonexistent statement 4 and omits statements 1 and 3.

Final answer: A