单选题 Ounce for ounce, blends of different artificial sweeteners match any individual artificial sweetener in sweetening power. When used to sweeten food, blends greatly decrease the likelihood that consumers will exceed acceptable daily intakes for individual sweeteners. Blends should therefore be used, rather than single sweeteners alone, since blends are clearly more healthful, yet equally effective.
The argument above depends on which of the following assumptions?

A、 When ingested together, different artificial sweeteners in the blends do not interact in a way that makes them harmful to human health.
B、 Different artificial sweeteners, when used together in food, do not contribute a more desirable flavor to the food than would any one of them by itself.
C、 The acceptable daily intake for any given artificial sweetener is a conservative figure that could probably be greatly exceeded at little or no risk.
D、 Consumers who substitute artificial sweeteners for sugar in their diets generally keep track of their daily intake of different sweeteners.
E、 (E) The ill effects on health produced by the intake of excessive quantities of any single artificial sweetener cannot be reversed by reducing intake later.

【正确答案】 A

【答案解析】[解析] 本题是由一个事实而得出一个结论：“Blends should be used”，并且又对得出的这一结论进行了解释“since blends are clearly more healthful，yet equally effective”。一般地，当原因放在结论之后表示强调原因的重要性或惟一性。所以上述推理成立所依赖的假设应为“除了A以外没有别的原因影响B”，若混合物一块消化时，不会相互作用以至于对健康有害，如(A)所说，就是一个很好的假设。可以对(A)进行取非验证，即若混合物一起消化会产生负作用，那么上面的“Blends should be used”必然不对，所以(A)必定正确。