如图，在棱长均为2的正四棱锥中，点E为PC的中点，则下列命题正确的是（  ）（正四棱锥即底面为正方形，四条侧棱长相等，顶点在底面上的射影为底面的中心的四棱锥）

A：，且直线BE到面PAD的距离为

B：，且直线BE到面PAD的距离为

C：，且直线BE与面PAD所成的角大于

D：，且直线BE与面PAD所成的角小于      But some people can't hear any sound at all. Some are born deaf. Others can hear well in their childhood, nut too many loud sounds hurt their ears later on.
       Many people in China can't hear ordinary sounds clearly. Lots of them are children. Most of them are born with good hearing. But six children of every 1,000 have hearing problems when they are born. And if a children has hearing problems, he or she usually will also have some learning problems at school.
        A lot of things can cause fearing problems, like, too much earwax is not good for our hearing. And noise louder than 85 decibels (分贝) can hurt our ears and make us lose our hearing for a short time or even for ever.
Hearing is important for all of us. So we should do our best to give our ears special care. Don't forget to do the following:
◎ Try to stay away from places with too much noise. If you have to go, wear earplugs.
◎ When swimming, remember to put earplugs into your ears to stop water from getting in.
◎ Never put anything sharp into your ears. If you think you have too much earwax, ask your parents to help you clean it out.
     Keep these things in mind. Then you won't be saying “WHAT? WHAT?” when you are older.