A、Three. B、Four. C、One. D、None. A题干询问文章中提及的导致火灾的原因有几个。文章第一句为中心句，caused by为关键词。有三个原因，即carelessness，laziness and stupidity。故答案为A。

(26) Many a fire is caused by carelessness, laziness and stupidity. Many people are careless about the problems of electric appliances, while some others want to save money and so they try to fix the problem by themselves instead of asking a service man. Fire that is caused by such behaviors is an example of stupidity. (27) Some smokers carelessly leave behind cigarettes which are being lighted in the ashtray. They go to do a piece of work that they remember all of a sudden. They want to come back to the cigarette when the work is done. Unfortunately, they forget their cigarettes which they have been smoking just then. (27) Some fire accidents are caused by burning cigarettes. Some people are lazy. They often throw away old newspapers and magazines in the kitchen where oil gas is stored. Big fire may take place when a child plays with matches there. Therefore, (28) old newspapers and magazines should not be put in the kitchen and matches should be placed beyond the reach of children. Some residents of tall apartment buildings fix theft-proof iron bars across the windows of their homes. They have not thought of them as obstacles to themselves on case of an outbreak of fire. Time and time again, those bars have been killers in fire accidents. The Fire Prevention Bureau has often told us to help to cut down fire accidents by reporting to the Fire Brigade, when staircases and exits are found to be obstructed. Without our cooperation, more fire accidents would likely happen.