The paragraph is followed by an incomplete phrase or sentence which summarizes the main idea of the paragraph. Choose the missing words of the phrase or sentence.  

Consumers of electricity usually accept the fact that power cuts frequently occur during thunderstorms. If outages(电力中断)occur on a sunny day, consumers will blame the power company. However, most outages occur due to circumstances beyond the power company’s control. Animals with the ability to reach the top of power poles can knock out power of many houses.
There are many （） for power failure.