The appropriate answer is a. the conversion of radiant energy to chemical energy. Plants use light from the sun to convert carbon dioxide and water to glucose. An important bi-product of this reaction is oxygen which is vital to all life on earth. When humans consume glucose and do work they are converting chemical energy into heat energy and mechanical energy.
6-C (breaks off)
7-C(they secrete acid that breaks away rocks)
7: symbiotic relationship
8: mutualism
9: commensalism
An example of an dramatic environmental event can be deforestation, or it can be animals losing their homes.
Because an antibody is "made" relative to the antigen, but kept at low levels when you are exposed the first time ("primary immune response"). The second time you're exposed to the same antigen, memory cells recognize it and the body produces a high level of antibodies, and the level of antibodies usually remains higher for a longer time ("secondary immune response"). This is your basic immune response (primary and secondary).
This explains exactly why vaccines are effective to extremely effective.