(i) The color of the blood is red because of the presence of haemoglobin. Haemoglobin is a pigment which is found in the red blood cells. Even the color of RBCs is because of the presence of haemoglobin in them. It is useful as four molecules of oxygen combine to one molecule of Haemoglobin and thus help in oxygen transport. 

(ii) Blood do not clot in our blood vessels because of the presence of a natural anti coagulant Heparin which is released by the basophils and the mast cells in our body. Hence, unclotted blood comes out from the site of injury even when platelets are present. 

(iii) There are three types of blood cells found in human beings. They are: red blood cells, white blood cells and the platelets. Different types of cells have different function. The type of blood cells which protect us from various kinds of infections in our body are the White Blood Cells or the Leucocytes. They are phagocytic in nature and hence, eat up the infection causing agent. 

(iv) Sumay must be very serious before doing anything. But at least he realized it before doing anything dangerous.