各位,我想问下,在做data sufficiency题目时,有些问题是一般疑问句的形式,例如:121. In the xy-plane, region R consists of all the points (x,y) such that 2x + 3y ≤ 6. Is the point (r,s) in region R ? (1) 3r + 2s = 6 (2) r ≤ 3 and s ≤ 2 类似这样的问题,怎么样才算条件充分呢?什么时候"NO"对于这类问题也是一种回答呢? 不好意思,我思维有点混乱。。。麻烦大侠们帮我解答下这个疑惑吧。。。谢谢!