Last year John earned________his brother did，who has a better position in a bigger company.

A．twice as many as　

B．twice as much as

C．twice as more as　

D．twice much as

水由喷嘴射出，已知流量Q=0.4m³/s，主管直径D=0.4m，喷口直径d=0.1m，水头损失不计，求作用在喷嘴上的力。