题目内容：
回答题。C
You wake up in the morning, the day is beautiful and the plans for the day are what you have been looking forward to for a long time．Then the telephone rings, you say hello, and the drama starts,The person on the other end has a depressing tone in his voice as he starts to tell you how terrible his morning is and that there is nothing to look forward to．You are still in a wonderful mood? Impossible!
Communicating with negative people can wash out your happi-ness．It may not change what you think, but communicating long enough with them will make you feel depressed for a moment or a long time.
Life brings ups and downs, but some people are stuck in the wrong idea that life has no happi-ness to offer．They only feel glad when they make others feel bad．No wonder they can hardly win others' pity or respect.
When you communicate with positive people, your spirit stays happy and therefore more positive things are attracted．When the dagger(匕首) of a negative person is put in you,you feel the heavy feeling that all in all, brings you down.
Sometimes we have no choice but to communicate with negative people．This could be a co-worker, or a relative．In this case, say what needs to be said as little as possible．Sometimes it feels good to let out your anger back to the negative person, but all this does is to lower you to that same negative level and they won't feel ashamed of themselves about that.
Negativity often affects happiness without even being realized．The negative words of another at the start of the day can cling to (附着) you throughout the rest of your day, which makes you feel bad and steals your happiness．Life is too short to feel negative．Stay positive and avoid negativity as much as possible.
The purpose of the first paragraph is to__________. A．make a comparison
B．offer an evidence
C．introduce a topic
D．describe a daily scene
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