We were in Grade 3. It was Easter. We had an Easter party. We played many games. We looked for Easter eggs. We ate chocolate eggs. We were so happy. ①

We were in Grade 4. We Visited Mr. MacDonald's farm. We saw a lot of animals. They were cows，horses，hens and sheep. There were many fresh vegetables，too. We ate tomatoes. They were good. ②

We were in Grade 5. My grandpa made a robot. His name is Robin. He is hard-working. He is very clever. He can speak English and Chinese. He can cook too. But he can't swim. ③

We were in Grade 6. There were many clubs. We sang and danced in the music club. We drew pictures in the art club. We made cakes in the cooking club. We had so much fun in our school! ④

如图是光学显微镜的一组镜头，①②为目镜标有5×字样和15×字样，③④为物镜标有10×和40×字样。则用此组镜头要达到最大放大倍数时所选用的镜头组合是

根据短文内容，选择正确最佳答案。
American Classroom Rules
1. If the teacher asks a question, you should give an answer. If you do not understand the question, you should put up your hand and ask the teacher to repeat the question. If you don't know the answer, it's all right to tell the teacher that you don't know. Then he or she knows what you need to learn.
2. There is no excuse for not doing your homework. If you can not go to school, you should call your teacher or your classmate and ask for the homework. It is your responsibility（责任）to find out what homework you have missed. It is not the teacher's job to remind you of missed homework.
3. You must not be absent(缺席) on a test day. If you are badly ill, call and let the teacher know you will not be there for the test. If your teacher allows you to take a makeup, you should take the test within one or two days after you return to class. Bad illness is the only reason for missing a test.
4. Be on time! It's not polite to be late. Also, it bothers other students. If you must come in late, be sure to do it quietly. Have your books out of your bag before you come into the classroom. Then go to your seat and sit quietly. In the US, it is not necessary to knock at the door before you come into the classroom.