跪求lawyer的 充分必要条件类型 解题方法解释!!!

earlytear

Although computers can enhance people’s ability to communicate, computer games are a cause of underdeveloped communication skills in children. After-school hours spent playing computer games are hours not spent talking with people. Therefore, children who spend all their spare time playing these games have less experience in interpersonal communication than other children have.
The argument depends on which of the following assumptions?
正确选项

(C) Children who do not spend all of their after school hours playing computer games spend at least some of that time talking with other people.
运用方法：     排除充分条件出现，必要条件不出现的可能


这道题到底哪个部分是充分条件，哪个部分是必要条件？
哪位大神能不能具体分析下是如何运用lawer说的方法的




还有一题

Ifthe county continues to collect residential trash at current levels, landfillswill soon be overflowing and parkland will need to beused in order to create more space. Charging each household a fee for eachpound of trash it puts out for collection will induce residents

to reduce the amount of trash they create; this charge will therefore protect theremaining county parkland.[c1]

Whichof the following is an assumption made in drawing the conclusion above?

[c1]条件型结论

Ifthe county continues to collect residential trash at current levels, landfillswill soon be overflowing and parkland will need to beused in order to create more space. Charging each household a fee for eachpound of trash it puts out for collection will induce residents

to reduce the amount of trash they create; this charge will therefore protect theremaining county parkland.[c1]

Whichof the following is an assumption made in drawing the conclusion above?

(C)[The collection feewill not induce residents to dump their trash in the parklands illegally 排除充分条件出现，必要条件不出现

sdcar2010

For necessary assumption, you can use the negation method instead.

That said, what the statement "排除充分条件出现，必要条件不出现的可能" means is that the necessary assumption will "remove those possibilities when a certain sufficient condition would not lead to the desired necessary condition in the argument."

In the first example, if those children who has some spare time other than playing computer games would not spend any of that spare time talking with other people, then the conclusion in the arguement is wrong. Sufficient condition: those children who has some spare time other than playing computer games ; necessary condition:  spend spare time talking with other people.

earlytear

感谢解答，可是还是没能系统理解如何看出充分条件 必要条件是什么