Considering that Chris asked those adults the question "What method of transportation do you use to get to work?", this question is not biased, since it is not leading to one or other correct answers.
Also, since the research concerns the method of transportation used by downtown workers, the population consists exclusively of downtown workers. And they were chosen randomly, so the sample is not biased.
Therefore, the graph describing this research is a reasonable estimator for the whole population of interest.
And from the graph, we see that cars were the most popular method of transportation for that sample.
Therefore, the correct answer is:
The claim is probably valid. The sample is not biased because the sample includes randomly selected members of the population and the question is not biased.