阅读下面短文，从A、B、C、D四个选项中，选出最佳选项。

    Julie is my aunt and she works at a radio station. She 1 it is an interesting job. Today I ask her about 2 life.     

    She says she is very busy from Monday to Friday. She goes to work at 7:30 and 3 at 20:00. Then she watches TV 4 half an hour. She goes to bed at 21:00. On Saturdays, she either plays tennis 5 goes swimming. They are 6 for her. What does she 7 do on Sundays? She always goes to the dance club. She is good at 8. My last question is not easy for her. I ask, “You like dancing. 9 not be a dancer?” She says, “I likes to talk to people through (通过) the 10. I can help more people in this way. Dancing is just my hobby (爱好), not my job.”

4.5gSiO₂晶体中含有的硅氧键的数目为 ____

骑自行车是一种时尚、环保的运动，深受人们的青睐．如图所示，下列关于自行车的说法正确的是（　　）