A. When

B. Why

C. in

D. What

Mike: ____ is your favourite season ，Sarah?

Sarah: Summer.

Mike: ____ do you like summer?                               

Sarah: Because we wll have a party at home 0n Children's Day.       

Mike: ____is Children's Day?                                

Sarah: It's ____ Jane.

如图所示，两个固定的等量异种电荷，在它们连线的垂直平分线上有a、b、c 三点，则（   ）