题目

设，，是实数，则“”是“”的（ ）A.充分不必要条件 B.必要不充分条件C.充要条件 D.既不充分也不必要条件 答案：【答案】B【解析】依据充分条件和必要条件的定义可得正确选项.当，时，不成立，即充分性不成立；当时，则，故，即必要性成立．即“”是“”的必要不充分条件．故选B．Public Speaking TrainingGet a coach__1.__，so get help. Since there are about a billion companies out there all ready to offer you public speaking training and courses, here are some things to look for when deciding the training that's right for you.Focus on positivesAny training you do to become more effective at public speaking should always focus on the positive aspects of what you already do well. Nothing can hurt confidence more than being told that you aren't doing well. _2.__， so good public speaking training should develop those instead of telling you what you shouldn't do.__3.__If you find a public speaking course that looks as though it's going to give you lots of dos and don'ts, walk away! Your brain is so full of what you're going to be talking about. _4.__. As far as we're concerned, there are basically no hard and fast rules about public speaking. Your audience can be your friends.You are a special person not a cloneMost importantly, good public speaking training should treat you as a special one, with your own personal habits. __5._. Your training course should help you bring out your personality, not try to turn you into someone you're not.A．You aren't like anybody elseB．You already do lots of things wellC．Turn your back on too many rulesD．Check the rules about dos and don'tsE．Whatever the presentation, public speaking is toughF．The one thing you don't want is for them to fall asleepG．So trying to force a whole set of rules into it will just make things worse