根据短文理解, 从所给的A、B、C、D四个选项中选择最佳答案填空。
In the United States, "hitting the books" means studying a subject with great effort.
One of the greatest challenges for students is taking tests. Students 1 long hours preparing for a test. They read all their books carefully, and then read them a second time and a third time. They 2 they know all the material the teacher has offered and prepare for every possible question. They study every night. They are "hitting the books".
In the United States, most children go to school 3 they are 5 years old. Public education is free and most children go to schools near their homes. School in these early years is 4. The children learn to read and write, but they also play games and go on trips. There is no 5 for them to hit the books at such an early age.
This situation changes as children become older. The subjects become more difficult. Students must 6 world history, physics and the life sciences. Tests become more common.
Pressure is 7 to hit the books, study hard, and advance（升级）. However, most serious students only really begin 8 the books for long hours when they reach high school.
High school students who hope to continue their education at a college or university 9 take a special test called the SAT. If they get a 10 score on the test, they have a good chance to enter a top American college. For this reason, many students hit the books for months to prepare for the SAT.
All this adds up to a lot of work-"hitting the books". Knowledge is a prize that is not easy to gain.
