一般来说，同一个体内牙根最长的是哪一组牙
A．上颌尖牙B．上颌双尖牙C．上颌磨牙D．下颌双尖牙E．下颌磨牙
参考答案：A
The dam was not strong enough to _____ the flood waters. The people living there had to remove from their houses.[ ]
A. hold down
B. hold back
C. hold off
D. hold on
堤岸防护工程可选用（）。
A.坡式护岸
B.坝式护岸
C.墙式护岸
D.其他防护形式
