A.She didn't understand what Jane was saying. B.Jane should have been more active. C.Jane needs training in public speaking lessons. D.Jane didn't seem to be nervous at all during her presentation.
【简答题】随着人们生活水平的提高,家庭厨房使用能源(燃料)的方式日趋多样化.我市某小区的居民中有使用电、煤饼和管道煤气等的家庭,其中管道煤气的主要成分是丙烷(C 3 H 8 )、丁烷(C 4 H 10 )(丙烷、丁烷在空气中燃烧的产物是二氧化碳和水),煤的主要元素成分是碳.有关电、管道煤气、煤的热值和价格如下表所示(为方便计算,个别数据作了适当处理): (1)请写出丙烷或丁烷在空气中燃烧时的化学反应方程式:...