You are writing an essay on how the lives of elephants in zoos differ from the lives of elephants in the wild, and you need to cite an effective quotation.

which quotation from a research source could you use in your essay?

a)
"one of the most important parts of zoo design is insuring the safety of the zoo's human visitors."

b)
"zoos usually close for different reasons than financial ones since zoos rarely lack for admission sales."

c)
"several studies have indicated that elephants held in captivity tend to exhibit signs of stress such as endless pacing."

d)
"zoos are places where people who would otherwise never get to see a wild animal from africa will actually get to see one."