Điền từ :
NATURE’S LIGHT
When you see a fire fly flitting through the air on a dark summer (33) _____, you may wonder (34) ______ the source of its light. This light (35) ______ from a mineral called phosphorus, which is found in small amounts in the (36) _____ of the firefly. Phosphorus is also found in the bodies of many (37) _______ of deep-sea fish. Sometimes (38) ______ a large number of these fish congregate near the surface of the ocean, their bodies illuminate an area that can be (39) _____ for long distances.
Phosphorus is also found in many parts of our bodies (40) _______ is essential to human life. In modern times, many vital uses have been found (41) _____ this mineral. Large amounts of phosphorus are utilized in medicines, in agriculture, and in manufacturing.
Perhaps (42) ____ most generally familiar (43) _____ to find phosphorus is in the heads of matches. Because phosphorus burns violently (44) ______ low temperatures, the small amount of heat produced by the friction of ru
ing the head of a match (45) _____ a rough surface is sufficient to (46) ______ the phosphorus in the match head to burn. As the head of the match ignites, it lights the wood or paper that forms the (47) ____ of the match
