题目

下列化学反应属于氧化还原反应的是 A  Na2CO3+Ca(OH)2＝CaCO3↓+2NaOH   B  AgNO3+NaCl＝AgCl↓+NaN03 C  H2SO4+Ba(OH)2＝BaSO4↓+2H2O      D  4NH3+5O2=4NO+6H2O 答案：DJack is late again. It is ___ of him to keep others waiting. A. normal　　　　 B. Ordinary　　　 C. common　　　　　 D. typical