先通读下面短文，掌握其大意，然后在短文后面各题所给的A、B、C选项中选出正确答案。
(A)
Lisa is a teacher and her husband is a doctor. They are both very 1and have no time to do all the housework. So she asks her children to do some 2 according to their age. She asks John, the elder brother in the 3, to do the dishes. It is an easy chore 4 the 15-year-old boy. And she asks Dave, her 5 son, to take the dog for a walk every evening. The two boys also have to help 6 the car when it is dirty. And they clean their tables, 7 their beds every day and 8 food in the market every Sunday morning. The boys can cook easy meals 9 their parents are not at home.
The family of 10 live in a big house 11they do all the housework by themselves. Lisa says, “When I was young, my father wanted us 12 with housework and learn how to 13 ourselves. Now I'm doing it to my kids.” John says, “Doing chores is 14.You can learn important life 15 and responsibility (责任).”
四种元素中只有一种是金属，下列说法错误的是（ ）