To tell the truth, what you said was too ________ for us to understand.

A．complex

B．comfortable

C．concrete

D．common

下列有关物质的化学式、名称、俗名完全正确的是[ ]

A．NaOH、氢氧化钠、纯碱

B．NaCl、氯化钠、食盐

C．CCl₄、甲烷、沼气

D．Na₂CO₃、碳酸钠、火碱