Graham purchased a bag of fertilizer at the hardware store to improve the state of his front lawn. he noticed three letters on the bag: npk. what do those letters stand for?

Nitrogen (N) , Phosphorus(P)  and Potassium (K)

Explanation:

In the constituents section of a fertilizer bag, NPK along with some numerical values such as 10-15-20 etc is mentioned.  

This NPK signifies the constituents of the fertilizer where N stands for Nitrogen, P stands for Phosphorus and and K stands for Potassium.  

Also the number such as 10-15-20 signifies the percentage amount of NPK with in the fertilizer such as a fertilizer bag of mark 10-15-20 contains 10 % nitrogen, 15 % phosphorus and 20% potassium.  

4.) metal

"-the movement of carbon from the nonliving environment into living things and back to the environment

-carbon is the essential component of proteins, fats, and carbohydrates (which make up all organisms)

-carbon exists in air, water, and living organisms

-producers convert carbon dioxide in the atmosphere into carbohydrates during photosynthesis

-bacteria in the atmosphere cycles through the system in filtration units

-in cellular respiration, carbon is released back into the atmosphere as carbon dioxide

-some carbon is stored in limestone (forming one of the largest "carbon sinks" on earth)

-largest carbon reservoir on earth= limestone

-carbon stored in the bodies of organisms as fat, oils, or other molecules may be released into the soil or air when the organism dies

-this may form deposits of coal, oil, or natural gas (fossil fuels, which increased the atmospheric carbon dioxide)

-fossil fuels store carbon left over from bodies of organisms that died millions of years ago

-they are located in the surface of earth, deep within the earth and beneath the ocean floor."