题目内容：
根据以下材料，回答题Exercise Can Replace Insulin (胰岛素 ) for Elderly Diabeties (糖尿病)
Most older people with so-called type II diabetes could stop taking insulin if they would do brisk exercise for 30 minutes just three times a week, according to new medical research results reported in the Copenhagen newspaper Berlingske Tidende on Monday.
Results from tests conducted on diabetics at the Copenhagen Central Hospital Rigshospitalet's Center for Muscle Research showed that physical exercise can boost the body's ability to utilize insulin by 30 per cent, the newspaper reported.
This is equal tol the effect most elderly diabetics get from their insulin medication today, it said.
Researchers had a group of non-diabetic men and a group of men with type II, all more than 60 years of age, exercise on bicycles six times a week for three months. After the three months the doctors measured how much sugar the test subjects' muscles could utilize as a measure for how well their insulin worked.
Associate Professor Dr. Flemming Dela of the Muscle Research Center said the tests demonstrated that the exercising diabetics had just as high insulin utilization as the healthy non-exercising persons.
"This means that the insulin works just as well for both groups. Physical exercise cannot cure people of diabetes, but it can eliminate almost all their symptoms. At the same time it can put off the point at which they have to begin taking insulin or perhaps completely avoid insulin treatment."
Dela was quoted as saying.
Insulin is a hormone produced by the pancreas, controlling sugar in the body and used against diabetes.
Dela said that to achieve the desired effect diabetics need only exercise to the point where they begin to work up a sweat, but that the activity has to be maintained since it wears off after five days without sufficient exercise.
Most diabetics realize that they have to watch their diet while remaining unaware of the importance of exercise, Dela added.
How could most elderly type II diabetics stop taking insulin? A．By taking more salt than usual.
B．By taking less salt than usual.
C．By doing brisk exercise for half an hour at least three times a week.
D．By going climbing, swimming or boxing every day.
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