单选题 What's the engine that drives American business? Innovation? Sweat? Capital? Try coffee. From the shop floor to the boardroom, Java—and I don't mean the soft ware—fuels workers and shapes office culture. What's more, a steaming cup of coffee may be as good for your health as it is for the bottom line. Many people take their coffee with a small dose of guilt, worried that it isn't good for the body. That's a misunderstanding from studies done in the 1950s and 1960s showing that coffee drinkers were prone to heart disease and other sufferings. These studies failed to account for cigarette smoking, which once went hand in cup with coffee drinking. Since then, the medical community has done a gradual turn on the health effects of coffee. Large, long-term studies show that coffee doesn't promote cancer and may even protect against some types. It's safe for the heart—so safe that the American Heart Association says it's OK for heart attack survivors to have a cup or two a day even as they recover in the coronary care unit. Results from the long-running Health Professionals Follow-Up and Nurses' Health studies show that drinking coffee cuts the risk of dying early from a heart attack or stroke. It's possible that the bean improves productivity, too. A bit of caffeine wakes up millions of workers in the morning. Controlled laboratory experiments indicate that it causes feelings of well-being and increases energy, alertness, and motivation. Functional MRI scans show that coffee activates parts of the brain involved in short-term memory, the kind that helps focus attention on tasks at hand. For all that, a word of warning is in order. The average cup of coffee serves up about 100 milligrams of caffeine, and a large specialty coffee can deliver five times that much. If you aren't used to caffeine, it can make you restless, boost your blood pressure, and dehydrate you. But the biggest health hazard is the extra stuff that drinkers add to coffee. Taken black, coffee is a nearly calorie-free beverage full of antioxidants and other vegetable nutrients. Add cream, sugar, fresh cream, and flavorings, and it turns into a fat- and calorie-laden dessert, which can add pounds that offset any possible health benefits. For most people, though, the health and social benefits of coffee outweigh the hazards, and the daily grind keeps American business spreading.

单选题 It can be inferred from Paragraph 1 that coffee _____.

单选题 The studies in the 1950s and 1960s misunderstood coffee because they _____.

单选题 According to Paragraph 4, the benefits of caffeine include _____.

单选题 The word "offset" (Line 6, Para. 5) is closest in meaning to _____.

单选题 It can be learned from the last paragraph that_____.