I am still confused of the correct answer. Don't you think "D" is the correct one? Can anybody help me?
(D) Do not give the antibiotic to all people who are sick.
This is the real-world medical advice: only prescribe when necessary. Many illnesses are viral (antibiotics don’t help at all). If antibiotics are given only when really necessary (not to everyone), fewer resistant strains develop, and the body’s natural microbes aren’t needlessly destroyed. This directly reduces both negative effects.
Fewer antibiotics → less resistance + less damage to natural microbes.
(E) Changing the antibiotics used every few weeks.
The idea here: rotating antibiotics may make it harder for bacteria to evolve resistance, but bacteria can still adapt, and this doesn’t stop killing natural microbes — in fact, they still get wiped out each time by exposing patients to multiple drugs. Also, "every few weeks" sounds like giving antibiotics constantly, which is unrealistic.
You may think switching antibiotics prevents resistance (true in theory for hospitals with long-term treatments). But the question asked about both harms: resistance and killing natural microbes. You only focused on the “resistance” part and ignored the second harm. Therefore, I think only "D" addresses both.