下列有关物质的俗名正确的是（　　）

A．Na₂CO₃→纯碱、小苏打

B．CuSO₄→胆矾、蓝矾

C．KAl（SO₄）₂•6H₂O→明矾

D．Fe₃O₄→磁性氧化铁

The device that allows a floating ship to sway without bending the marine riser system is the（）.

A.yaw joint

B.sway joint

C.slip joint

D.flex or ball joint