correct answer please

D Question 15 1 pin Peng Is studying the relationship between amount of sleep and virens level. He sends out a compulsory survey to the students In his MATH1005 class, Which of the following could be a source of blas? Consent bias: only consenting students fill out the survey O All of the other responses O Observer bias: Peng may report based results G Selection blas: only students in one class are surveyed D Question 16