Sample 1: Students in a single sorority. - This is not a good representative sample because the number of people in a single sorority is not indicated and there could just be a few students in that single sorority.
Sample 2: Students majoring in public health. - This is not a good representative sample because it is more likely that the students in this major are more conscious of their eating habits than a usual college student.
Sample 3: Students who participate in intercollegiate sports. - This is also not a good representative sample because of the same reason in Sample 2. Athletes are more likely to be conscious of their dietary habits to maintain their sporty skills.
Sample 4: Students enrolled in a required history class. - Out of the 4 samples, this is the most likely choice as a good representative sample because the students enrolled in a required history class are more varied and everyone has to take it hence the word "required". Everyone means any student in college, may it be a math major, health major, etc.