题目

I'm new here．Could you tell me        ，please? A．when does the first bus arrive B．when the first bus arrives C．when did the first bus arrive D．when will the first bus arrive 答案：B吸气时的描述正确的是（　　） A、膈肌收缩，肺扩张B、膈肌收缩，肺收缩C、膈肌舒张，肺收缩D、膈肌舒张，肺扩张