Michelle is taking an antibiotic to treat a bacterial infection. She notices her medicine is not working as well as it used to, so she starts taking higher dosages. Eventually, the medicine does not appear to have any effect on the infection at all.
What is the most likely reason Michelle's medication has stopped working?
a
The bacteria have built up a resistance to Michelle's antibiotic.
b
Michelle's antibiotic has built up a resistance to the bacteria.
c
Michelle's immune system has built up a resistance to the bacteria.
d
The antibiotic has built up a resistance to Michelle's body.