I just wonder _______that upsets him so much.

A．what it is

B．what he does

C．how it is

D．why it does

10g含有杂质的CaCO₃和足量的盐酸反应，产生CO₂0.1mol，则此样品中可能含有的杂质是[ ]

A．KHCO₃和MgCO₃

B．SiO₂和MgCO₃

C．K₂CO₃和SiO₂

D．无法确定