题目

a=3是直线ax+2y+3a=0和直线3x+（a-1）y=a-7平行且不重合的__________. 答案：解析：当a=3时，l1:3x+2y+9=0,l2:3x+2y+4=0.∴l1∥l2,反之若l1∥l2,则a（a-1）=6,即a=3或a=-2,但a=-2时，l1与l2重合.答案：充要条件LONDON - A British judge on Thursday sentenced a businessman who sold fake (假冒的) bomb detectors (探测器) to 10 years in prison, saying the man hadn't cared about potentially (潜在的) deadly consequences.It is believed that James McCormick got about $77.8 million from the sales of his detectors ---which were based on a kind of golf ball finder---to countries including Iraq, Belgium and Saudi Arabia. McCormick, 57, was convicted (判罪) of cheats last month and sentenced Thursday at the Old Bailey court in London. "Your cheating conduct in selling a great amount of useless equipment simply for huge profit promoted a false sense of security and in all probability materially contributed to causing death and injury to innocent people," Judge Richard Hone told McCormick. "You have neither regret, nor shame, nor any sense of guilt."The detectors, sold for up to $42,000 each, were said to be able to find such dangerous objects as bombs under water and from the air. But in fact they "lacked any grounding in science" and were of no use. McCormick had told the court that he sold his detectors to the police in Kenya, the prison service in Hong Kong, the army in Egypt and the border control in Thailand."I never had any bad results from customers," he said.小题1: Why was McCormick sentenced to prison?A．He sold bombs.B．He caused death of people.C．He made detectors.D．He cheated in business.小题2: According to the judge, what McCormick had done _______.A．increased the cost of safeguardingB．lowered people's guard against dangerC．changed people's idea of social securityD．caused innocent people to commit crimes小题3:Which of the following is true of the detectors?A．They have not been sold to Africa.B．They have caused many serious problems.C．They can find dangerous objects in water.D．They don't function on the basis of science.小题4:It can be inferred from the passage that McCormick _______.A．sold the equipment at a low priceB．was well-known in most countriesC．did not think he had committed the crimeD．had not got such huge profit as mentioned in the text