Many infectious diseases are becoming difficult to treat because of bacterial
resistance to antibiotics. Populations of bacteria can become resistant when they are
exposed to an antibiotic. What is the best general explanation for how this occurs?
The antibiotic induces specific mutations in some of the bacteria that make them
antibiotic-resistant.
The antibiotic activates bacterial genes encoding enzymes that can destroy the
antibiotic.
The antibiotic increases the bacterial mutation rate, so that resistant mutant
bacteria are more likely to arise.
Antibiotic-resistant mutant bacteria already present in the population survive
and reproduce in the presence of the antibiotic.