适用于编写程控交换机中对实时性要求严格的程序语言是（）
A.SDL/GR
B.SDL/PR
C.MML
D.汇编语言
参考答案：D
Without facts , a person can’t form a correct opinion , for he needs to have actual knowledge _____ his thinking .
A．which to be based on
B．on which to base
C．which to be based
D．which to base
