A:在“点击”帧加上空白关键帧,按钮能正常响应
B:当按钮“按下”时,按钮将消失
C:此按钮无法响应鼠标的任何操作
D:“点击”帧中的内容是不显示的
抛物线y=ax2+c与x轴交于A、B两点,顶点为C,点P在抛物线上,且位于x轴下方.
Hi! I'm Nini. I'm a monkey. I like riding my bike. But I don't like skipping. Huanhuan is my brother. He likes basketball. I have(有)a good friend(朋友). Her name is Qiqi. She is a panda. She is fat. She likes table tennis.
根据短文内容选择正确的图片。
输电线的电阻为r,输送的电功率为P,用电压U送电,则用户得到的功率为( )