羊水过多孕妇进行腹腔穿刺时，放羊水一次量不能超过（）。

A.500mL

B.1000mL

C.1500mL

D.2000mL

E.2500mL

When navigating using DGPS（Differential Global Positioning System）you may expect your position to be accurate to within a radius of（）.

A.10 meters

B.20 meters

C.50 meters

D.100 meters