北京市为减轻大气污染，在汽车尾气排放口加装“催化净化器”，可将尾气中的有害气体CO、NO转化为参与大气循环的无毒混合气体，其反应的化学方程式可表示为：2CO+2NO
N2+2X，则X的化学式为（ ） 催化剂 .
A．O2
B．H2O
C．NO2
D．CO2
由题意，知反应的化学方程式为2CO+2NO
N2+2X，根据质量守恒定律的意义，则“2X”中含有2个碳原子、4个氧原子，故可知X的化学式为CO2． 催化剂 .
故选D．
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| By my third day in the hospital, I realized Tom didn't visit. I couldn't understand 1 my best friend wouldn't come to see me. Struggling against the 2 , I phoned his 3 . His mother answered, and when I asked for Tom, she got 4 . "He's not here right now," she said. I thought it was 5 that she didn't tell me where he was or 6 to have him call me. But I was so weak, I just let it 7 .I found out later that Tom's mother called my parents right after we rang 8 . My phone call really made her 9 , and she 10 they talk to me. Later that night, my mom 11 . Did I remember drinking? Did I remember in a car?I had 12 what she was talking about, so she finally told me the news: I'd hit a tree. Tom, in the 13 seat, was thrown from the car and killed instantly. The only reason I'd lived was because of my 14 . My first 15 was of shock.. I'd been drink-driving? Hit a tree? Killed Tom? I felt like the 16 person in the world. Even after I was able to 17 several weeks later, I didn't want to eat, I didn't want to talk. I just 18 at the wall in my 19 and cried. The only person I wanted to see was Tom. I didn't feel like 20 with any of my old friends. | ||||
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