A pathogenic strain of bacteria has become resistant to an antibiotic that once could kill it. What has happened to these bacteria to make this happen? (4 points) a
The bacterial cells learned to remove the receptors on their cell surfaces, making it impossible for the antibiotic to attack them.

b
Most of the bacteria make changes to their DNA to protect themselves, making themselves immune to future attacks.

c
Some of the bacterial cells were able to produce toxins against the antibiotics, making them more likely to survive.

d
Only the few bacteria that were immune to the antibiotic survived and reproduced, making all their offspring immune to it as well.