In a town with a population of 45,000 people, 60 percent of the voters are registered as democrats. In a sample of 1,500 voters randomly chosen for a survey, 70 percent were registered as democrats. Which statement best describes why the sample was NOT valid? a. The sample was chosen at random. b. The sample included many more people than was necessary. c. The sample was not representative of the voters registered as democrat. d. The sample did not include all the voters in the city.