In a large city school system with 20 elementary schools, the school board is considering the adoption of a new policy that would require elementary students to pass a test in order to be promoted to the next grade. The PTA wants to find out whether parents agree with this plan. If they randomly select one of the elementary schools and contact every parent by phone, what kind of bias is there?A. bias due to the use of a voluntary response sampleB. response bias due to desire to give acceptable answersC. undercoverage bias due to a poor sampling frameD. no biasE. nonresponse bias