“种粮补贴”惠农政策的出台，大大激发了农民的种粮积极性，某粮食生产专业户去年计划生产小麦和玉米共18吨，实际生产了20吨，其中小麦超产12％，玉米超产10％．该专业户去年实际生产小麦、玉米各多少吨？
（1）根据题意，甲和乙两同学分别列出了如下不完整的方程组：
甲：$\left\{\begin{array}{c}x+y=\_\_\_\\ \frac{x}{1+12\%}+\frac{y}{1+10\%}=\_\_\_\_\end{array}\right.$  乙：$\left\{\begin{array}{c}x+y=\_\_\_\\ 12\%x+10\%y=\_\_\_\_\_\end{array}\right.$
根据甲、乙两位同学所列的方程组，请你分别指出未知数x，y表示的意义，然后在上面的横线上分别补全甲、乙两位同学所列的方程组：
甲：x表示　        　，y表示　       　；
乙：x表示　        　，y表示　       　
（2）求该专业户去年实际生产小麦、玉米各多少吨？（写出完整的解答过程，就甲或乙的思路写出一种即可）

下面四种说法中代表一个生态系统的是  (    )

完形填空

Most American families are smaller than those in other countries. They have one or two （1）________ and one or two children each.

Children in the US will（2）________ their parents' house when they grow up. They usually live（3）________ their parents because of work. They often（4）________ to their parents or telephone them. And they often go to visit their parents when they are（5）________ vacation.

Parents usually let their children choose their（6）________ jobs. Americans think it's （7）________ for young people to decide their future by themselves.

Parents also （8）________ their children to do some housework at home. And in many families, children are paid for （9）________ housework. Parents think it can help them learn（10）________ to make money for their own use.