有一已充电的平行板电容器，若使它带的电荷量减少3×10^-4 C，其电压降为原来的三分之一，求电容器原来带的电荷量。

—May I come in? I'm sorry I'm late.  

—Come in, please. But could you tell me         ?[      ]

A. how do you come to school     

B. what were you doing then      

C. who you talked with      

D. why you are late