上下平面间分别分布有ε₁=ε₀，ε₂=4ε₀两种介质，在垂直分界面两侧分别有点电荷q₁和q₂，如题1-61图所示，则二电荷连线与分界面相交处ε₂介质中点的电场强度E_A为（）。

A．A

B．B

C．C

D．D

— How long do you want me to heat the oil?

— Heat it till it _____ to smoke. [ ]

A. would begin

B. begins

C. will begin

D. began