椭圆$\frac{x^2}{a^2}+\frac{y^2}{b^2}=1\left(a>b>0\right)$的离心率为$e=\frac{1}{2}$，右焦点为$F\left(c,0\right)$，方程$a{x}^2+bx-c=0$的两个实根分别为$x_1$和$x_2$，则点$P\left(x_1,x_2\right)$（　）

在盛有2毫升淀粉糊的试管中注入2毫升唾液溶液，振荡后，放在37℃的温水中保温10分钟．取出试管冷却并滴入2滴碘酒，结果试管内不变蓝，该实验说明淀粉（　　）​

汽车从制动到停止下来共用了5s，这段时间内，汽车每1s前进的距离分别是9m，7m，5m，3m，1m．求汽车前3s和全程的平均速度．

    It is not often that a person has sympathy for someone who stole from him / her. But when Chrissy Marie read the note written by the brother of the “1” who took her butterfly wind chime(风铃), her heart2.

    The young boy 3 the note and left it on her doorstep. Chrissy4 a photo on Facebook of the note and the US＄5 the little boy5.

    The note read: “I am6 that we stole your wind chime. Our mum died and she liked butterflies. My sister 7 it to put by our window. I am sorry this is the only 8I have. Please do not be mad at us. Jake.”

    Chrissy Marie wants Jake and his sister to know she is not9 Now Chrissy wants to find Jake and his sister and10their money.

    Chrissy 11 to Jake via her Facebook message: “Well Jake, I hope you can come to get your money 12. I had three of those wind chimes. And I am not mad at all.”

    Chrissy is13 to the area, so she doesn't know many people. She tried to 14who Jake is or where he lives, but 15

    “I have knocked on a few doors nearby. But I can't 16 far because of my injured leg.” she wrote. “I asked my neighbour,17 she didn't know anyone named Jake.”

    Chrissy understands how 18 it can be to lose a mother. She said, “Obviously, the boy felt 19 for what his sister did.”

    Chrissy has been surprised by all the20 her post got, and she hopes it won't scare Jake off.