— 12,500 kilometres is too long a journey!

— Yes.            the journey was long and hard, the Red Army (红军) pushed on. [ ]

A. Though

B. Because

C. As

D. While

充实水柱是指由水枪喷嘴起至射流90%的水柱水量穿过直径为（）圆孔处的一段射流长度。

A.250mm

B.300mm

C.350mm

D.380mm