____
从方框中选出下列各旬的最佳应答语。
A.It was good.Thank you.
B.Yes.I could see many stars.
C.I rode a bike yesterday.
D.We went there by plane.
E.I'm 34 kg.
如图1所示为用电火花打点计时器验证机械能守恒定律的实验装置.
一元二次方程x2﹣4x+4=0的根的情况是( )