Which of the following situations could be used to produce an unbiased random sample? a-surveying students in a college psychology class to find out preferred majors of students at that school. b-asking people at the local supermarket what their favorite brand of ice cream is to find out what the preferred brand of ice cream is in that city. c-survey every tenth audience member leaving the american country music awards and ask what their favorite type of music is. d-finding the heights of all 9th grade female students at a high school and using it to determine the average height of all girls at the school.