下列属于条件反射的是 [ ]
A．婴儿吃奶
B．膝跳反射
C．缩手反射
D．学生听到铃声，进入教室
D
--- Do you know who designed the CD-ROM Around the World in Eight Hours?
--- Yes. It ______ by Nancy Jackson.
A．has designed
B．designed
C．designs
D．was designed
用足量的氢气还原2克氧化铜，可得到金属铜多少克？
