十三写作13，七十一写作17。

钛铁合金是生产链条钢、锚链钢等的重要原料，如果要比较钛（Ti）和铁的金属活动顺序，以下方法不能达到目的是（　　）

现在长颈鹿的颈部都很长，这是由于（　　）的结果。

龙舟比赛是中国传统运动项目之一如图，某队龙舟和运动员总质量为2.5×10³kg，在一次龙舟赛上，该队以1min40s的成绩夺得500m比赛冠军．已知该龙舟在运动过程中受到的阻力是龙舟和运动员的总重力的0.12倍．

（1）该队的龙舟比赛在500m比赛过程中的平均速度是多少米/秒？

（2）如果把在比赛过程中该队龙舟的运动看作匀速直线运动，求运动员在比赛过程中划船时的功率是多少千瓦？（g=10N/kg）

阅读短文，判断正误。
Dear Joe,
    How are you? My sister and I are having our holiday. Yesterday we went to the library. We got there by bus. We read storybooks and had lunch there. The food was delicious. It was cheap, too. We went shopping in the afternoon. I bought a pair of shoes. I was very tired. We are planning to learn skating and do many other things during the holiday. We are sure we'll have a good time.
    How about your holiday? Please write to me soon.
Miss you.
Alice