单选题 In recent years, there has been a steady assault on salt on from the doctors: salt is bad for you—regardless of your health. Politicians also got on board. "There is a direct relationship," U. S. congressman Neal Smith noted, "between the amount of sodium a person consumes and heart disease, circulatory disorders, stroke and even early death. " Frightening, if true! But many doctors and medical researchers are now beginning to feel the salt scare has gone too far. "All this hue and cry about eating salt is unnecessary," Dr. Dustan insists. "For most of us it probably doesn't make much difference how much salt we eat. " Dustan's most recent short-term study of 150 people showed that those with normal blood pressure underwent no change at all when placed on an extremely low salt diet, or later when salt was reintroduced. Of the hypertensive subjects, however, half of those on the low-salt diet did experience a drop in blood pressure, which returned to its previous level when salt was reintroduced. "An adequate to somewhat excessive salt intake has probably saved many more lives than it has cost in the general population," notes Dr. John H. Laragh. "So a recommendation that the whole population should avoid salt makes no sense. " Medical experts agree that everyone should practice reasonable "moderation" in salt consumption. For an average person, a moderate amount might run from four to ten grams a day, or roughly 1/2 to 1/3 of a teaspoon. The equivalent of heart problems may have to limit dietary salt, if their doctor advises. But even the very vocal "low salt " exponent, Dr. Arthur Hull Hayes, Jr. , admits that "we do not know whether increased sodium consumption causes hypertension". In fact, there is increasing scientific evidence that other factors may be involved: deficiencies in calcium, potassium, perhaps magnesium; obesity(much more dangerous than sodium); generic predisposition; stress. "It is not your enemy," says Dr. Laragh, "Salt is the No. 1 natural component of all human tissue, and the idea that you don't need it is wrong. Unless your doctor has proven that you have a salt related health problem, there is no reason to give it up. "

【正确答案】 A

【答案解析】解析：根据文中第二段的“Of the hypertensive subjects，however，half of those onthe low-salt diet did experience a drop in blood pressure，which returned to its previouslevel when salt was reintroduced．”可知，低盐饮食使患有高血压的研究对象的血压下降。因此，根据Dr．Dustan的研究，我们可以推断出可以限定某些人食用低盐饮食。A项正确。