When we are asked to draw an inference on the GMAT, we are looking for something that must be true based on the statements above. In this case, the stimulus contains two sentences that contain information. What can we determine to be true based on those statements?

A) Although the text indicates that increases in the length of muscles can reduce the risk of injury, it never says that the injury will be completely eliminated. Accordingly, we cannot say that this statement must be true.
B) Although the text indicates that stretching and drinking water reduces the risk of injury, we cannot conclude that people who do not do so have a high risk of injury. Perhaps the base risk of injury is 10 percent whereas stretching and drinking water reduces it to 4 percent. We really have no way of knowing what the pre-stretching risk is. Accordingly, we cannot say that this choice must be true.
C) Although the text indicates that stretching and drinking water reduces the risk of injury, we have no way of determining that this is the best way. The text provides no information about other methods or indications that this is superior than any other method.
D) This modest claim is completely supported by the text. Some people will get some benefit from stretching and drinking water. This is the credited response.
E) The text doesn't say this. The text says that stretching and drinking water will result in some benefit.

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The above question seems to be a permutation of this official GMAT question:

Increases in the level of high-density lipoprotein (HDL) in the human bloodstream lower bloodstream cholesterol levels by increasing the body's capacity to rid itself of excess cholesterol. Levels of HDL in the bloodstream of some individuals are significantly increased by a program of regular exercise and weight reduction.

Which of the following can be correctly inferred from the statements above?

(A) Individuals who are underweight do not run any risk of developing high levels of cholesterol in the bloodstream.
(B) Individuals who do not exercise regularly have a high risk of developing high levels of cholesterol in the bloodstream late in life.
(C) Exercise and weight reduction are the most effective methods of lowering bloodstream cholesterol levels in humans.
(D) A program of regular exercise and weight reduction lowers cholesterol levels in the bloodstream of some individuals.
(E) Only regular exercise is necessary to decrease cholesterol levels in the bloodstream of individuals of average weight.