Which of the Following Is NOT a Possible Reason That

Which of the following is NOT a possible reason that Asian student math scores are higher than those of students in the United States?

A) U.S.students are more prone to learning disabilities.
B) Asian parents are more likely to help their students with homework.
C) Asian teachers spend more time teaching math than U.S.teachers do.
D) Asian students spend more days in school than U.S.students do.