There are advantages and disadvantages to 21 Asian and Western educational method. For example, one advantage 22 the education in Japan is that students there learn much more math and science 23 American students. They also study more hours each day than Americans 24 . The study is difficult, but it 25 students for a society that values discipline (纪律) and self-control. There is, however, a disadvantage. Memorization is an important learning method in Japanese schools, 26 many students say that after an exam, they forget much of the information that they have memorized.
The advantage to the education in North America, 27 the other hand, is that students learn to think by themselves. The system prepares them for a society that values 28 ideas. There is, however, a disadvantage. When students graduate from high school, they haven't memorized 29 many basic rules and facts as students in other countries 30 .
21.

A. not only
B. all
C. both
D. only