下列物质,放在空气中容易变质的是

A．硫酸钠(Na₂SO₄ )

B．氢氧化钠(NaOH)

C．碳酸钠(Na₃CO₃)

D．食盐(NaCl)

_____ the general state of his health，it may take him a while to recover from the operation.

A．Given

B．To give

C．Giving

D．Having given