题目

One year ago. I asked a worker to help me repair my old house. He had a bad first day on the job: his car broke on the way, then he found he had left his tools for work at home and his wife telephoned to say his son had a bad cold. While I drove him home, he was silent all the way. When arriving, he invited me to meet his family.As we walked towards the front door, he stopped at a small tree, and touched the tree with hands. When we opened the door, I was very surprised to see he changed into another person and there was a big smile on his face instead. He hugged (拥抱) his son and gave his 下列两种气体的分子数一定相等的是 A．质量相等、密度不等的O2和C2H4     B．等体积等密度的CO和C2H4 C．等温等体积的O2和N2                D．等压等体积的N2和CO2