Mrs ,Taylor has ___8-year-old daughter who has _____gift for painting –she  has won two national prizes.

A．a, a

B．an ,the

C．an ,a

D．Th

将小灯泡L₁和L₂（均不考虑灯丝电阻变化）并联接到电压为U的电源两端，它们都正常发光，此时L₁和L₂的电功率分别为P₁和P₂（）。若把L₁和L₂串联接到另一电源两端，要求L₁和L₂两端的电压均不超过各自的额定电压，则串联时电路两端的最大电压为______。