You are grownup now, so it's up to you to decide whether to________English or French.[ ]

A. take off  

B. take on

C. take in  

D. take up

下列物质间转化都能通过一步实现的是

A．Si→SiO₂→H₂SiO₃→Na₂SiO₃

B．Al→Al₂O₃→NaAlO₂→Al(OH)₃

C．S→SO₃→H₂SO₄→SO₂

D．N₂→NO₂→HNO₃→NO