The growing speed of a plant is influenced by a number of factors,   ________are beyond our control. [      ]

A. most of them      

B. most of which

C. most of what      

D. most of that

在数据库的三级模式结构中，内模式的个数

A．只有1个

B．与用户个数相同

C．由系统参数决定

D．有任意多个