阅读下面短文，从短文后所给各题的四个选项([A]、[B]、[C]和[D])中选出能填入相应空白处的最佳选项。

Some students at the Open University left school 20 years ago. (36) are younger but all must be at least 21 years old. This is one example of (37) the Open University is different (38) all the others. Its students must (39) work fulltime or be at home all day. They do not have to (40) any examinations before they are (41) . This is why the university is called "open". It was started (42) order to help people who (43) having a university education when they were young. The first name (44) the open university was "the University of the Air". The idea was to teach (45) the air, in other (46) , on radios and the television. (47) of the teaching is done like this. The student also receives (48) at one of 283 study centers in the country. He must also (49) three weeks every summer as a (50) student. Tutors and students (51) and study together, (52) in other universities. At the end of the Open University’s first year, the (53) were good; three (54) of four students passed their examinations. (55) they do this every year, they will finish their studies in four or five years.