5.A in the light B by virtus C with the exception D for the purpose
For example,it has long been known that total sleep 6 is 100 percent fatal to rats,yet,7 examination of the dead bodies,the animals look completely normal.A researcher has now 8 the mystery of why the animals die.The rats 9 bacterial infections of the blood, 10 their immune systems-the self protecting mechanism against diseases had crashed.
Vitamins are organic compounds necessary in small amounts in the diet for the normal growth and maintenance of life of animals, including man.They do not provide energy, 11 do they construct or build any part of the body.They are needed for 12 foods into energy and body maintenance.There are thirteen or more of them,and if 13 is missing a deficiency disease becomes 14 .Vitamins are similar because they are made of the same elements-usually carbon,hydrogen,oxygen,and 15 nitrogen.They are different 16 their elements are arranged differently,and each vitamin 17 one or more specific functions in the body. 18 enough vitamins is essential to life,although the body has no nutritional use for 19 vitamins.Many people, 20 ,believe in being on the "safe side"ad.thus take extra vitamins.However,a well balanced diet will usually meet all the body’s vitamin needs.
6. A reduction B destruction C deprivation D restriction
7. A upon B by C through D with