题目

    People have been painting pictures for at least 30,000 years. The earliest pictures were painted by people who hunted animals. They used to paint pictures of the animals they wanted to catch and kill. Pictures of this kind have been found on the walls of caves in France and Spain. No one knows why they were painted there. Perhaps the painter thought that their pictures would help them to catch these animals. Or perhaps human beings have always wanted to tell stories in pictures.     About 5,000 years ago the Egyptians and other people in the Near East began to use pictures 对于反应：H- + NH3 ＝ H2 + NH2-的正确说法是(　 )。　 Ａ．属于置换反应　　　　　 Ｂ．H-是还原剂Ｃ．NH3是还原剂　　　　　 Ｄ．H2既是氧化产物又是还原产物