先天性幽门梗阻必须行手术治疗。()
参考答案：对
The teacher said that _______ of the boys would take part in the talent show. [ ]
A. three five
B. three fives
C. thirds fifths
D. three fifths
滚摆在上升过程中 ____ 能逐渐减小，__________能逐渐增加．滚摆在下降过程中_________能逐渐减小，____ 能逐渐增加，若没有摩擦阻力 __________总和不变．
