To determine whether voters would be willing to vote for a tax increase to improve the city's parks, the park commission surveys 500 park users. Why is this sample likely to be biased? A:Park users are too busy to be bothered with surveys. B: The entire population of the city was not surveyed. C:Park users are more likely to be willing to pay more to improve parks. D:There are not enough people in the sample.

Given that To determine whether voters would be willing to vote for a tax increase to improve the city's parks, the park commission surveys 500 park users.

Sampling to give accurate estimate about the population should have the following criteria

1) strictly random

2) Should cover all types of people in the population

3) Sample size should be a reasonable proportion of population.

Here the population is entire voters.

But people surveyed were the visitors of the park. Obviously visitors are interested to improve city parks. But the remaining population will not be favourable as they would think this is additional burden.

Thus the sample taken is biased.

Hence answer is

C:Park users are more likely to be willing to pay more to improve parks