单选题 The legal limit for driving after drinking is 80 milligrams of alcohol in 100 milliliters of blood when tested. But there is no sure way of telling how much you can drink before you reach this limit. It varies with each person depending on your weight, your sex, if you've eaten and what sort of drinks you've had. Some people might reach their limit after only about three standard drinks. In fact, your driving ability can be affected by just one or two drinks. Even if you're below the legal limit, you could still be taken to court if a police officer thinks your driving has been affected by alcohol. It takes about one hour for the body to get rid of the alcohol in one standard drink. So, if you have a heavy drinking session in the evening, you might find that your driving ability is still affected the next morning, or you could even find that you're still over the legal limit. In a test with professional drivers, the more alcoholic drinks they had had the more certain they were that they could drive a test course through a set of movable posts…and less able they were to do it! So the only way to be sure you're safe is not to drink at all. Alcohol is a major cause of road traffic accidents. One in three of the drivers killed in road accidents have levels of alcohol which are over the legal limit, and road accidents after drinking are the biggest cause of death among young men. More than half of the people stopped by the police to take a breathalyzer(呼吸测醉器) test have a blood alcohol concentration more than twice the legal limit. 6. Can people be sure how much they can drink below the legal limit