Bob would have come to the airport to see us off, but he _____. [ ]

A. is will

B. had been ill

C. was ill

D. will be ill

测定亚铁盐含量时为避免干扰，应选择

A．重铬酸钾法

B．高锰酸钾法

C．铈量法

D．容量沉淀法

E．碘量法