题目

Raj is a 35-year-old man. He wasn't good with his parents.Raj was on a trip with his wife and his son, he met a small boy aged about 10 years old selling toys. The boy asked Raj to buy something. Raj asked the boy why he sold toys. The boy said, A year ago, my father lost one hand. He cannot work now. My mother works as a maid (女仆) in a few houses. I wanted to help my parents by selling these toys. I go to school in the morning, and sell toys in the evening. I work for 3 hours a day and study at night!”Raj bought a few toys from the little boy. He thought about what the boy said. He real19．下列有关反应现象的描述正确的是（　　）A．蜡烛燃烧时产生大量黑烟B．硫酸铜溶液中加氢氧化钠溶液产生蓝色沉淀C．燃着的木条在二氧化碳中燃烧更旺D．盐酸和石灰石混合生成二氧化碳