According to the National Postsecondary Student Aid Study conducted by the U.S. Department of Education in 2008, 62% of graduates from public universities had student loans. We randomly sample college graduates from public universities and determine the proportion in the sample with student loans. For which of the following sample sizes is a normal model a good fit for the sampling distribution of sample proportions?

A. 10
B. 20
C. 30
D. both 20 and 30
E. none of these