(2) Gum swelling and bleeding is caused by scurvy, which is caused by the lack of vitamin C in the body. Sailors can't eat ⅳ fruits and vegetables during long-term sea voyage, which leads to vitamin C deficiency.
(3) Only the small intestine in human digestive tract contains enzymes for digesting I fat, and the digestion of fat needs the help of bile. The digestion process is as follows: fatty bile lipase glycerol+fatty acid.
(4) Teenagers in the growing period should eat a reasonable diet, and eat more foods rich in protein, calcium, phosphorus and vitamins, which are II, III and IV in the figure.
So, the answer is: (1) sugar; Oral cavity; glucose
(2)Ⅳ
(3) small intestine; Fatty bile lipase glycerol+fatty acid
(4)Ⅱ、Ⅲ、Ⅳ