关于圆周运动的说法，正确的是（） A．做匀速圆周运动的物体，所受合力一定指向圆心
题型：选择题
问题：
关于圆周运动的说法，正确的是（ ）
A．做匀速圆周运动的物体，所受合力一定指向圆心
B．做圆周运动的物体，其加速度可以不指向圆心
C．做圆周运动的物体，其加速度一定指向圆心
D．做圆周运动的物体，只要所受合力不指向圆心，其速度方向就不与合力方向垂直
题型：选择题
Ask just about any college student you know,and he is likely to tell you that he is a member of facebook.com.Many students say they check their e-mail.It’s so popular “facelooking”has become a verb “Everywhere everyone is doing it,”college student Katie Silverman 
said,“It’s like everyone’s center of life.”
Facebook is an online social meeting place where students create profiles (简介)，share personal information, and meet other members. It is password protected and targeted to high school and college students;members must have an edu.email address to join.
Many students say it has changed their social lives, giving them an easy way to find and chat with classmates who share their interests.“Some people might be too shy to go t
o talk to someone they like in one of their classes,but on facebook it’s a lot easier to strike
up a conversation,”said Rahul Vanjani.
The website was founded by two Harward University students who wanted to meet more of their classmates.It became so popular that the website is at 2,200 colleges and at 22,000 high schools.It says that it has 6 million active users,two—thirds of whom are on it every day.Many of the facebook members said their parents had 
no idea they were on it .“No way.My parents certainly don’t know about it,” said a college senior who asked us not to use his name.
To keep it popular,Facebook says it stops students posting improper information.Some students have paid the price.At Fisher College in Boston,two students were kicked out for using facebook.com to do something th
at is against the law.At North Carolina State University,four students were punished for posting photos about drinking.
小题1:The passage is mainly about____.
A．student’s idea about Facebook
B．the development of Facebook
C．the popularity of Facebook with students
D．the rules of Facebook小题2:To become a member of Facebook,you must_____.
A．have an edu,e—mail dress
B．have your own profile
C．be a high school student
D．offer main personal information小题3:By saying “
Some students have paid the price”in the last paragraph,the author means more students_____.
A．will have to pay money for being on Facebook
B．always use Facebook to do something against the law
C．have been punished for doing some improper things on Facebook
D．often stop others from posting improper information on Facebook小题4:We can learn about Facebook from the passage that______.
A．the information that students offer to Facebook is secret to others
B．Facebook is at more colleges that at high schools
C．6 million active users of Facebook are on it every day
D．many students don’t want their parents to know they are facebooking