Antibiotic resistance in bacteria occurs because:
(a) The bacteria need to resist the antibiotics and so evolve mechanisms that will help them do this.
(b) Variation in the bacterial population allows some of the bacteria to produce antibiotic resistant materials while others can not.
(c) Variation in the bacterial population allows some of the bacteria to survive an inadequate dose of antibiotics and pass these variations on to the next generation.
(d) Variation in bacteria allow some to avoid detection by host immune systems and then pass on these variations to the next generation.
