题目

假如你是一名航天员，驾驶飞船登上月球，想探测月球表面附近是否有磁场，下列工具中最理想的是( ) A . 灵敏电流表 B . 灵敏电压表 C . 灵敏指南针 D . 灵敏温度计 答案：C All flights ________ because of the snowstorm, the passengers couldn't help but take the train．Because all flights ________ due to the snowstorm, the passengers could help but take the train． A．had been canceled B．have been canceled C．having been canceled D．being canceled