How can existing satellites predict volcanic eruption? A．They use monitoring systems to detect the presence of specific gases. B．They use sensors to detect the presence of specific gases. C．They detect the presence of specific gases by gathering data on the earth's volcanoes. D．Their orbits allow them to observe the entire earth and predict volcanic eruptions.
A.They B. B．They C. C．They D. D．Their E.
【参考答案】
B 现在的卫星如何预测火山爆发?[A]卫星使用监控系统检测特定气体的存在。[B]卫星使用传感器检测特定气体的存在......