1. which of the following is a physical change? (2 points) an iron chair rusts when left outside a sample of water boils and releases gas. a plant changes carbon dioxide and water into sugar. a newspaper burns when placed in a fire.

the answer to your question is:

c. complementary base-pairing

trachea, alveoli, lung capillaries, arteries

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.