根据汉语写单词。

抛物线y=2x²上两点A(x₁,y₁)、B(x₂,y₂)关于直线y=x+m对称，且$x_1·x_2=-\frac{1}{2}$，则m等于（   ）

①电离辐射       ②紫外线       ③煤焦油       ④肿瘤病毒        ⑤苯．

    It was a hot summer day. The sun was shining brightly and all could think of was1down with a scoop of my favorite ice cream. I decided to make a quick2to the newly opened ice cream parlor (冰淇淋店) close by for a mid-day3.

    As soon as I arrived there, I 4my ice cream in a fancy cone and asked the server to5two tubs of chocolate ice cream for folks at home.

    While waiting for my take-out, I was halfway through my icy treat and was enjoying the view of the two colorfully6ice cream flavors, sitting pretty one next to the other.

    Now that my to-go order was7, I headed to the payment counter to settle the bill. Surprisingly, the cashier had forgotten to8my ice cream,9only for the two tubs.

    The next few10passed by as I11between doing what was easy—clearing the bill and moving out, and doing what was right—12 the error. I knew if I didn't bring the error in the bill to his13, my ice cream would be charged against his14.

    That moment, my decision was made and I went and told him what he had 15. He looked at me in 16 and thanked me profusely for telling the error. Had it not been for my 17telling the error, he would have been 18. The smile of relief on his face made me smile, too.

    I came out of the ice cream parlor feeling really19about myself. I knew that day how wonderful it feels to do what is right20what is easy.