What Is the Best Explanation as to Why the U

What is the best explanation as to why the U.S.has a lower percentage of adults with a college education than many other countries?

A) The high cost of a college education in the prevents many from attending college.
B) Poor math and science performance among U.S.high school students prevents many from getting into college.
C) U.S.colleges are more academically difficult than colleges in other countries.
D) None of these choices are correct.