牙根变异最多的是（）。
A.上下前牙
B.上下双尖牙
C.上下第一磨牙
D.上下第二磨牙
E.上下第三磨牙
参考答案：E
He _______ for two years. We are still sad about his _______.
A．died, dead
B．died, death
C．has been dead, dead
D．has been dead, death
