题目

A giant helium（氦） balloon is telling residents of Paris how good or bad the air quality is．When it’s good, the balloon ----measuring 22 meters wide and 32 meters high---shines green．_________, it’s red．        A．Though terrible                      B．Whenever good               C．If worse                    D．When bad 答案：D 解析: 略某导体接到6 V电压下，它消耗的功率是6 W；将改接到3 V的电压下，这个导体的功率是    W．