题目

在密闭容器中进行下列反应：M(g)＋N(g)  R(g)＋2L， 此反应符合下面图像，下列叙述正确的是(    ) A. 正反应放热，L是固体或液体       B. 正反应放热，L是气体 C. 正反应吸热，L是固体            D. 正反应吸热，L是气体 答案：B—Doesn’t he feel       impolite when he laughs with his mouth full of food? —I will ask him to pay attention to his behavior. A．it                B．that              C．this              D．these