What is the meaning of the word "catalyst" as it is used in the following sentence? tragedies are often a catalyst that causes communities to come together.

a a common enemy
b a complex chemical reaction
c something that causes a change
d an event that makes people sad

Twenty years gone, and i am back again on my own island. as for my change of skin, that is a charm athena, hope of soldiers, uses as she will; she has the knack to make me seem a beggar man sometimes and sometimes young, with finer clothes about me. it is no hard thing for the gods of heaven to glorify a man or bring him low. —the odyssey, homer based on what odysseus says in the passage, what has he learned? humans can become like gods. humans are under the gods’ control. humans can change from beggars to soldiers.