When released into the atmosphere, the refrigerant Freon damages the Earth’s ozone layer. A new kind of refrigerant does not have this effect. The manufacturer claims that replacing Freon with the new refrigerant in both new and existing refrigerators will prevent any further Freon damage to the ozone layer apart from that being done by the Freon already in the atmosphere.
Which of the following must be true if the manufacturer’s prediction is to prove accurate

A．Freon can be replaced with the new refrigerant without releasing any Freon into the atmosphere.

B．The damage already done to the ozone layer is not of environmentally significant proportions.

C．The atmosphere can reverse the damage to the ozone layer caused by the past use of Freon.

D．The new refrigerant can counteract the damaging effects of Freon on the Earth’s atmosphere.

E．(E) The new refrigerant causes no environmental damage of any kind when it is released into the atmosphere.

某一电解电容器标注的是：“300V，5μF”，这表示（　　）

A．电容器必须在300V电压时才能正常工作

B．要使两板间电压降低1V，它所带的电量必减少5×10^-6C

C．电容器只有在带电时电容为5μF

D．只有当电压是300V时，电容才是5μF