在下列反应中，既属于离子反应又属于氧化还原反应的是（    ）

A．BaCl₂溶液和K₂SO₄溶液反应

B．点燃H₂和O₂的混合气体

C．NaOH溶液和CuSO₄溶液反应

D．Zn放入盐酸中

John's success has nothing to do with good luck. It is years of hard work      has made him what he is today.

A．why

B．when

C．which

D．that