DS,顾名思义，强调数据的充分性，i.e.着重考察的是能不能得出唯一确定的结论而并不是取决于题目本身的答案的Yes or no,如：问：a>b?条件：a=0,b=1数学常识告诉我们答案是a<b,但因已知条件已足够充分且唯一明确（Compared with the case in which more than one solution are employed）能推出该结论是错误的，故它具有充分性，记住结论：能使你得出唯一确定答案的（No matter the answer is yes or no）条件即为充分条件。就该题而言：the first premise:n+3是质数，则n+3一定是奇数，则n是大于2的偶数，故的出n不是质数的唯一确定结论，故条件（1）充分 the same case applies to the 2nd condition:n-1是质数，则n-1是奇数，则n是偶数且>2,则可推出n不是质数，同样充分地得出了唯一确定的答案。故应选(D) either is sufficient. Hope it helps!
To beauty or coupled with beauty ttss: Because the known conditions are so limited and the exact Q is not represened,I can just do some judgement accroding to my feeling as follows: Now that we have no reference ,let the expression you described as "含绝对值的有x的代数式" be |x+1|,the only way to determine wether the condition given is sufficient is to know the exact value of x since different xs can lead to respective results,a vague result. If you can elimate other possible keys and limit the value of x to a single number(not a variable such as x,y but a exact number 1,2,3, or constant a,b,c),the condition is sufficient.In one word,the answer must be definitely unique. The mere expression "2x",in itself,is not sufficient to let us know what the exact value it is since we can assign a large number of possibilities,even the whole real numbers. Hope it helps!
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发表于 2010-3-27 21:19:43
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