题目

The teacher apologized        late．  A．to his students to arrive    B．to his students for arriving C．at his students to arrive     D．at his students for arriving 答案：B2010年1月12日海地发生了7.0级的大地震．给人民群众造成了重大损失．因为地震产生的声波属于______（填“次声波”或“超声波”）．所以地震前人们并没有感知到．