已知矩形ABCD的顶点都在半径为4的球O的球面上,且AB=3,BC=2,则棱锥O-ABCD的体积为( )
A:51
B:351
C:251
D:651
关于北京的叙述,正确的是( )
填空.
Food is very important to our health. Everyone needs to eat well if he or she wants to have a strong body.Our minds, like our bodies, always need the best food. This kind of food is knowledge. We start getting knowledge when we are very young.