Vitamins 　　Vitamins are organic compounds which are present in certain foods and are essential to the health of men and other animals.__1__.Without these substances,the breakdown and absorption of foods could not occur.Certain vitamins participate in the formation of blood cells,hormones,nervous system chemicals,and genetic materials.__2__.Fat-soluble vitamins include vitamins A,D,E and K.The water-soluble vitamins include vitamin C and the B-vitamin complex. 　　Fat-soluble vitamins are usually absorbed with foods that contain fat.Excessive amounts of these vitamins are stored in the body's fat,the liver and kidneys.Because fat-soluble vitamins can be stored,they do not have to be consumed every day. 　　__3__.A deficiency of vitamin A leads to skin changes and night blindness,or failure of the eye to adapt to the dark.Vitamin A can be obtained directly from foods of animal origin such as milk,eggs,and liver.__4__. 　　Vitamin D acts muck like a hormone and regulates calcium and phosphorus absorption and metabolism.Some vitamin D is obtained from such foods as eggs,fish,liver,butter,and milk.But humans get most of their vitamin D from exposure of the skin to sunlight.A deficiency of vitamin D leads to bone problems. 　　The role of vitamin E in the human body has not been established.——__5__ Vitamin E is found in seed oil and wheat. 　　Vitamin K is necessary for the clotting of blood.It is produced in sufficient quantities by bacteria in the intestine,but is also provided by leafy green vegetables and eggs. 　　The water-soluble vitamins,C and B complex,cannot be stored and therefore need to be consumed daily to satisfy the body's needs.Vitamin C is important in the formation and maintenance of connective tissue.It protects gums,skin,and mucous membranes.It is mainly found in fruits like oranges. 　　B-complex vitamins serve a wide range of important metabolic functions and prevent some diseases.They are found mostly in the liver. 　　A.Vitamins are classified into two groups,that is,the fat-soluble(溶解脂肪的)and the water-soluble(溶解水的)vitamins. 　　B.Their functions are mainly to enhance the metabolism(新陈代谢)of proteins and fats. 　　C.It is necessary for a healthy life. 　　D.Vitamin A is essential for normal growth and for the health of epithelial cells. 　　E.It has been popularly advocated for a great variety of diseases,but no clear evidence exists that it eases any specific disease. 　　F.Vitamin A can also be obtained through eating green and yellow fruits and vegetables 　　标准答案：BADFE 　　1.B.B中的Their与前句中的Vitamins呼应;而后句的句意(没有这些物质,食物的碎化和吸收就不能进行。)揭示前句的内容应该是在谈论Vitamins的“好处”,同时B中metabolism与后句中提到的“食物的碎化和吸收”呼应。 　　2.A.A在句意上总领后面两句：后面两句分别是在对fat-soluble(溶解脂肪的)vitamins 和 water-soluble(溶解水的) vitamins进行解释。 　　3.D.该段的核心词(反复出现词)是vitamin A,而后句谈到vitamin A缺乏会造成的问题。在句意上与后句句意相关：一正(功效)一反(缺乏的后果)。 　　4.F.前句说到Vitamin A能如何被获得,而F在句意上与之相呼应：谈及Vitamin A“还能”怎样被获得。 　　5.E.空格前句说vitamin E在人体中的功能还没有被确认,后句说vitamin E在哪里能找到,同C相比,E更合理：E的句意也是表明vitamin E的“不确定的”功效,在句意上前后承接,而C只是笼统的说vitamin E是有必要的。