手机已经成为了人们日常必备品之一，低头看手机的“低头族”随处可见（图甲）．有研究发现，若玩手机时姿势不当，可能让颈椎承受多达27公斤的重压．为求证这一问题，某同学查阅相关资料，画出了“低头族”头部前倾某一角度时的模型（图乙），颈椎看成轻杆，颈部肌肉看成轻绳，头部看成质点，所受重力已标出．请在答卷的图丙中用平行四边形定则作出重力与颈部肌肉对头部拉力的合力，并根据所作的图测量颈椎承受的压力是头部重力的倍．（保留两位有效数字）

口腔上皮细胞和洋葱表皮细胞共有的结构是（  ）

____I am 73 years old. I often watch TV in my free time. Of all the programs, I like the news best. Through the TV, I can learn what is happening in our country and in the world. At seven every evening , I always sit in front of the TV.

____I am a grandma. I like Chinese traditional opera. From Monday to Thursday, I usually turn on the TV at half past seven. The programs from CCTV 7 are my best.

____I am a basketball fan. I like playing basketball very much. But I am too busy. So I have to watch it on TV. Every night, I watch the match till midnight. I am crazy about it , especially NBA.

____I am a housewife. I do the housework all day, I'd like to watch TV at night. I prefer to see soap operas like “Palace”, “Meteoric Garden” and so on. Because they can make me feel relaxed.

____I am the only son in the family. I am in Grade Five. I like cartoons best. I often watch cartoons on TV after doing the homework.

从所给的A、B、C、D、E选项中，选择正确的小标题。

A、  B、

C、   D、

E、