题目

下列物质与水反应会放出氧气的是    A．Na2O               B．Na2O2             C．K          D．NO2  答案：B解析: Perseverance is a kind of quality and that’s________it takes to do anything well. A. what 　　　　　　   B. that 　　　　　　　　 C. which 　　　　　　 D. why