题目

已知⊙O1与⊙O2相切，⊙O1的半径为9 cm，⊙O2的半径为2 cm，则O1O2的长是A．1 cmB．5 cmC．1 cm或5 cmD．0.5cm或2.5cm 答案：C解析:略       The conflict(争执) over what or how much homework should be comes partly from the fact that people can't seem to agree on the purpose of homework.      What teachers think?      Some teachers think that homework is necessary to reinforce(巩固)what is learned in school. And so they ask their students to memorize what was discussed in class through homework..     Some teachers think the point of homework is to cover material that the class didn't have time to get to, so their homework is to let students learn additional things.     Other teachers like homework simply because they want students to form work habits and still others believe homework is necessary because it is the best way for parents to learn what their children do in school.     Parents' ideas.     But many parents seem to have different ideas.     Elissa Cohen,who has twins at Lafayette Elementary School, doesn't like the fact that third-grade students in DC elementary schools are asked to write about 25 book summaries a year. “They do the same thing over and over without really getting into alternate(交替) ways of thinking about books and thinking about reading and writing. ”     Experts' opinions.     Some education reformers (改革者), such as Howard Gardner, a Harvard University, professor well-known for his theory on multiple intelligence(智力), think that Cohen is on the right track. But it is often hard to persuade overworked teachers to give much thought to homework tasks. 1.How many opinions do the teachers have on "homework"?   A. 3.            B. 4.          C. 5          D.6 2.According to the experts' opinions,   A. teachers should give necessary work to the students   B. teachers should not work too hard or too long   C. teachers should let the students repeat what they didn't have time to get in class   D. what Cohen's thinking about is correct 3.What's the problem with Elissa Cohen's twins in writing about their book report?   A. They find homework really hard.   B. They simply copy one repeatedly.   C. They aren't given much thinking about what they read.   D. They get different ways of thinking about their work.