Which best describes bias, if any, from the sample surveyed?

survey: favorite vacation locations
sample: randomly selected visitors to a national park

A.
Since the sample is randomly selected, there is unlikely to be any bias.

B.
Since the people surveyed are visiting a national park, they may be biased against vacations close to home.

C.
Since the people surveyed are visiting a national park, they may be biased towards national parks.

D.
Since a large number of people visit national parks, the sample should be large enough to eliminate any bias.