You want to know the opinions of dog owners across America on the issue of establishing a law requiring individuals who own pit bulls to obtain insurance for their dogs. You obtain a list of all registered dog owners and mail a survey to a random sample of 5,000 owners. Of those, 2,389 responded and 22% say that they favor the law. Which of the following statements is true?

Because random sampling is used, we can feel confident the percentage of all dog owners who say they favor insurance for pit bulls is close to 22%.
Because less than half of those who were mailed the survey actually responded, we can feel fairly confident that the actual percentage of all dog owners who say they favor pit bull owners getting insurance for their dog is close to 22%.
We cannot trust these results because the survey was mailed. Only survey results from face-to-face interviews are considered valid.
The results of this survey may be affected by nonresponse bias.