—Why don’t you go out to play, Rose?

—I’m afraid I can’t. I have much homework _________.

A．do

B．does

C．doing

D．to do

某元素A的气态氢化物的化学式为H₂A，则A的最高价氧化物的水化物的化学式为

A．H₂AO₃

B．HAO₃

C．H₂AO₄

D．H₃AO₄