Food is very important to our health. Everyone needs to eat well if he or she wants to have a strong body.Our minds, like our bodies, always need the best food. This kind of food is knowledge. We start getting knowledge when we are very young.
等质量的①CH4、②H2、③HCl、④SO2,在标况下体积由大到小顺序是( )
下图是一个DNA分子的片段,回答下列问题: