A、Because the quality of water decides its volume. B、Because health conditions affect the amount of water needed. C、Because ther

Many people believe they are supposed to drink eight glasses of water a day, or about two liters. Why? Because that is what they have been told all their life.  But a new report offers some different advice.  Experts say  people should obey their bodies; they should drink as much water as they feel like drinking.
    The report says most healthy people meet their daily needs for liquid by letting thirst be their guide. The report is from the Institute of Medicine, part of the National Academies.  This organization provides scientific and technical advice to the government and the public.
    The report contains some general suggestions.  The experts say women should get about two-point- seven liters of water daily.  Men should get about three-point-seven liters.  But wait--in each case, that is more than eight glasses.
    There is an important difference.  The report does not tell people how many glasses of water to drink.  In fact, the experts say it may be impossible to know how many glasses are needed to meet these guidelines.  This is because the daily water requirement can include the water content in foods.  People do not get water only by forcing themselves to drink a set number of glasses per day.  People also drink fruit juices and sodas and milk.  They drink coffee and tea.  These all contain water.
    As you might expect, the Institute of Medicine says people need to drink more water when they are physically active.  The same is true of those who live in hot climates.  Depending on heat and activity, people could need two times as much water as others do.
26. What does the new report advise people to do?
27.What function of the Institute of Medicine is mentioned in the passage?
28.Why do experts claim it impossible to know how many glasses of water are needed per day?