阅读下列短文,从每小题所给的A、B、C三个选项中选出一个最佳选项。

    People don't mind if you put your elbows or arms on the table when you are not eating. But once you have started eating, you should only rest your forearms(前臂) on the table. You should let your kids know that table manners are more than about proper eating. Teaching your kids the following table manners whether they are eating in a restaurant or at home:

◆You should use a fork unless the food is meant to be eaten with fingers.

◆You should not fill your mouth with food.

◆You should chew with your mouth closed. Nobody likes to see food being chewed up or hear it being chewed on. You should not talk while your mouths full of food.

◆If you want something that is out of your reach, then just ask someone to pass it on to you.

◆You should not pick anything out of your teeth. If something is troubling you very much, you can excuse yourself and go to the restroom to pick it out.

◆You should always use a napkin to wipe your mouth, which should be placed on your lap when you are not using it. You shouldn't wipe your face or your nose with a napkin, both are unpleasant.

◆If you are eating at someone's home, don't forget to express(表达) your thanks to the host. Also, tell him how delicious the food is, even if it isn't.

    No one is born a winner. People make themselves into winners by their own 1.

    I learned this lesson from a(n)  2 many years ago. I took the head 3job at a school in Baxley, Georgia. It was a small school with a weak football program.

    It was a tradition for the school's old team to play against the 4 team at the end of spring practice. The old team had no coach, and they didn't even practice to 5the game. Being the coach of the new team, I was excited because I knew we were going to win, but to my disappointment we were defeated. I couldn't 6 I had got into such a situation. Thinking hard about it, I came to 7 that my team might not be the number one team in Georgia, but they were 8me. I had to change my 9about their ability and potential.

    I started doing anything I could to help them build a little  10 .Most important, I began to treat them like 11 .That summer, When the other teams enjoyed their 12 ,we met every day and 13passing and kicking the football.

    Six months after suffering our 14on the spring practice field, we won our first game and our second, and continued to15.Finally, we faced the number one team in the state. I felt that it would be a 16for us even if we lost the game. But that wasn't what happened. My boys beat the best team in Georgia, giving me one of the greatest17my life！

    From the experience I learnt a lot about how the attitude of the leader can 18 the members of a team. Instead of seeing my boys as losers, I pushed and19them. I helped them to see themselves 20 ,and they built themselves into winners.

    Winners are made, but born.

如图所示，质量为2kg的金属块放在水平地面上，在大小为20N、方向与水平方向成37°角的斜向上拉力F作用下，从静止开始做匀加速直线运动．已知金属块与地面间的动摩擦因数μ=0.5，力F持续作用2s后撤去．（sin37°=0.6，cos37°=0.8，重力加速度g取10m/s²）．求：