题目

A train stopped at a small station. A man looked out of the window and saw a woman who was selling cakes. People from the train were buying them. The man wanted to buy a cake, but the woman was standing far from the window. It was raining, and the man didn’t want to go out in the rain. Suddenly he saw a boy who was walking on the platform(站台) not far from him. “Come here, boy!” the man said. “Do you know how much those cakes cost?” “Five cents for each,” the boy answered. The man gave the boy ten cents and asked him to buy two cakes. “One for me, and one for you,” he told在加热时，浓硫酸与铜发生反应的化学方程式为：2H2SO4（浓）+Cu   △  . CuSO4+SO2↑+2H2O对于该反应，下列说法中不正确的是（　　） A、是氧化还原反应B、铜是还原剂C、H2SO4表现了氧化性和酸性D、反应后铜元素的化合价降低