如图（a）所示,在光滑水平面上用恒力F拉质量为1kg的单匝均匀正方形铜线框,在1位置以速度v₀=3m/s进入匀强磁场时开始计时t=0,此时线框中感应电动势为1 V,在t=3s时刻线框到达2位置开始离开匀强磁场．此过程中v t图象如图（b）所示,那么（  ）

如图所示，水平放置、间距为d的两平行金属板A、B带有等量异种电荷，在离A、B板均为 $\frac{d}{3}$ 处有a、b两点．不计电场边缘效应，则（   ）

A: Hello, is this Mr. Rogers?

B: Yes, it is.____

A: I'm from the package delivery company (快递公司); I have your package. Are you at home?
B: Unfortunately I'm at work right now. ____

A: Actually, this package needs your signature (签名). Can I bring it to your office instead?
B:____I don't have time to leave my desk.

A: I see.____

B: Yes, that would be better. Can you bring it to my home at 6 p.m.?

A: Sure, that is fine. ____

B: Great, thank you so much!