当可逆反应2SO2+O2⇌2SO3达到一定限度后通入18O2，再经过一段时间，18O存在于（ ）
A．SO3、O2中
B．SO3、SO2中
C．SO3、SO2、O2中
D．SO2、O2中
可逆反应一定是同一条件下能互相转换的反应，如二氧化硫、氧气在催化剂、加热的条件下，生成三氧化硫；而三氧化硫在同样的条件下可分解为二氧化硫和氧气．故18O2中的18O通过化合反应存在于SO3中，SO3中的18O通过分解反应会存在于SO2中，最终SO3、SO2、O2中都含有18O．
故选C．
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| When I was 18,one morning, my father told me to drive him into a town ,about 18 miles away. I had just learned to drive , so I__1___ with pleasure. First we came to the town. Then I took the car to a nearby garage (汽车修理厂) to have it ___2___and promised(答应) to pick Dad up at 4 p.m. Because I had a few____3___ to spend ,I decided to go to the ___4___.However I became so interested in the films that I forgot the ___5___.When the last film finished ,it was 6 o'clock. I was afraid Dad would be ___6__and never let me drive again ,so I drove back ___7___ to meet Dad and made an excuse for my being late. I’ll never forget __8__ he gave me .“I'm disappointed (失望的) that you feel you ___9___lie (说谎) to me, Jake .I am angry ,not with you but with myself. I have failed ___10__ I have brought up (抚养) a son who can not even ____11___the truth to his own father .I am going ___12____ home now and think seriously about where I have gone wrong all these years.” Dad began walking along the road. I begged ___13___, telling him and drove___14___him for 18 miles ,at a speed of 5miles an hour .It was the most___15___lesson.I have never lied to him ever since. | ||||
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