未满12周岁的中小学生严禁骑自行车上下学。家离学校2公里之内的学生一般要步行上学。（）

正确答案：C
本题是一道假设型逻辑题。本题的逻辑主线为“所有骑自行车上学的学生都回家吃午饭一有些在郊区的学生不骑自行车上学”，若使假设推理成立，从结论入手，“有些在郊区的学生不骑自行车上学一有些在郊区上学的学生骑自行车一有些在郊区的学生回家吃午饭”，因为题目中的论证可以同时为真，因此，C项是必须假设的。其余选项均推不出。

答案：D

解析：

正确答案：C
本题是一道假设型逻辑题。本题的逻辑主线为“所有骑自行车上学的学生都回家吃午饭→? →有些在郊区的学生不骑自行车上学”，若使假设推理成立，从结论入手，“有些在郊区的学生不骑自行车上学→有些在郊区上学的学生骑自行车→有的在郊区的学生回家吃午饭”，因为I和O可以同时为真，因此，C项是必须假设的。其余选项均推不出。

答案：D

解析：

正确答案：
Ⅵ．Samplel Sally is at No. 14 Middle School. Her home is not far from school. She often goes to school by bike. Some- times she goes to school on foot. It takes her about fif- teen nunutes to school by hike. It takes her about thirty nunutes to school on foot. She is a good student: She doesn't like to be late. In the morning she gets up early and gets to school early. She studies very hard