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 occur.

a) The antibiotic induces specific mutations in some of the bacteria that make them antibiotic

resistant.

b) The antibiotic activates bacterial genes encoding enzymes that can destroy the antibiotic.

c) The antibiotic increases the bacterial mutation rate, so that resistant mutant bacteria are more

likely to arise.

d) Antibiotic resistant mutant bacteria already present in the population survive and reproduce in

the presence of the antibiotic