一工厂要将100吨货物运往外地，计划租用某运输公司甲、乙两种型号的汽车共6辆一次将货物全部运动，已知每辆甲型汽车最多能装该种货物16吨，租金800元，每辆乙型汽车最多能装该种货物18吨，租金850元，若此工厂计划此次租车费用不超过5000元，通过计算求出该公司共有几种租车方案？请你设计出来，并求出最低的租车费用．

最近和我国接壤的某些邻国因为国内民族矛盾激化，甚至发生了战争，而我国依然保持和平稳定，究其原因，是我国坚持了______的民族关系，和______民族原则。（     ）

①民族平等、团结、互助、和谐

②平等、团结、共同繁荣

③民族平等、团结、共同富裕

④ 平等、团结、互助、和平

    Many people think that twins are exactly the same. But some of them are not! Al and Mike are twin brothers. They look the same and in some ways they are the same. But in other ways they are different. Al and Mike are both very strong. Al and Mike both like soccer. But Al plays soccer every day and Mike plays soccer only on weekends. Mike likes watching soccer games on TV but Al only likes to play the game, not to watch it. Al and Mike are both outgoing and funny, but Mike is a little more outgoing than Al. Mike is also a little more serious about school. Al and Mike are very popular at school, and they both have a lot of friends.

根据短文内容判断正误.

实验器材：____．

实验步骤：____．