题干
Peter is busy ___________ at school, but he never forgets __________ exercise every day.
A：work, doing
B：working, to do
C：work, to do
D：working, doing
答案(点此获取答案解析）
B
2H2O ②H2CO3=H2O+CO2↑
Cu+H2O ④SO2+2NaOH=Na2SO3+H2O．
，
，若
，则实数
的取值范围是（ ）