已知f（x）在（﹣∞，+∞）内是减函数，且a+b≤0，则下列各式正确的是（    ）。填序号）①f（a）+f（b）≥f（﹣a）+f（﹣b）；    ②f（a）+f（b）≤f（﹣a）+f（﹣b）；

③f（a）+f（b）≥﹣f（a）﹣f（b）；      ④f（a）+f（b）≤﹣f（a）﹣f（b）．

If you came into contact with nitrobenzene while disconnecting the cargo hose，you should be aware that it is（）.

A.highly toxic when absorbed through the skin

B.a blood poison

C.a nerve poison

D.All of the above