A certain strain of bacteria used to be susceptible to penicillin. Today, that strain is resistant to penicillin. Which best explains this observation?
A. The bacteria needed to become resistant to survive.
B. The mutation rate in the bacteria population greatly increased.
C. The isolation of the strain caused it to become resistant.
D. A mutation occurred and was passed to future generations.

Idont really understand

Where are the following choices

The return of the wolf to yellowstone national park will probably affect the bird population to some degree, not significantly. while wolves will hunt birds when necessary, they prefer to hunt larger prey. the bird population will most likely only be affected when hunting is scarce for the wolves. birds of prey will also probably not be affected as much as other birds who spend more time on the ground hunting for food as the tend to spend more time in the air or in trees since they do not need to stay on the ground for long due to the nature of the way they hunt.