Vitamins, like minerals, are chemicals. There is absolutely not difference in the chemical structure (26)
of the nature vitamin C and the chemical structure (27)
of the synthetic vitamin C. Also, while most sub- stances are harmless at very low level of intake, all (28)
substance -- even the elements that are essential to life -- can be dangerous if you overdo them. Take water for example. Six or eight glasses a day will keep your body in good fluid balance. But you can also be drown (29)
 in it. Some people argue that individuals vary greatly (30)
 in their need for nutrients, it cannot necessarily be stated any given amount is too much; that is all (31)
relative. But since there is little solid information on what is the optimal intake of any essential nutrient in healthy individuals, it would be impossible to give guidelines that take these proportional needs into the (32)
 account. Just as with other drugs, the relation to (33)
 different vitamin dosages varies, with some people better able than others to tolerate large amounts. While we do know that very specifically what the toxic level (34)
 is for vitamins A and D, we are far less sure about vitamin E, even though it, too, is fat-soluble, and we still don’t understand the water-soluble vitamin, the C (35)
 and the B groups, which the body cant store.


答案:
26.not改为no
27.nature改为natural
28.at后加a
29.去掉be
30.that后加 
31.stated后加that 
32. 去掉the
33. relation改为reaction 
34.去掉that
35. vitamin改为vitamins