CAMBIOS GEOLÓGICOS Y BIOLÓGICOS
AZOICA PALEOZOICA MESOZOICA CENOZOICA ANTROPOZOICA

bacteria – a word that often brings out a sense of uneasiness in most of us are, in fact, one of the earliest forms of life. it can be quite unnerving to know that there are bacteria all over your skin, hair, and even inside the body. but only a few species of bacteria are dangerous. the majority of bacteria are good, and without them, life on earth wouldn’t be possible. let’s learn more about how are bacteria essential for you to survive.

i truly dont know the answer wait i do its 1,3,4

d. i assume the underlined word is "role." reformat if it isn't.

explanation:

role is closest to part because when replacing words, "playing a vital decision," "playing a vital activity," and "playing a vital dollar" don't make logical sense. the only meaningful choice is "playing a vital part."

this fits one of merriam-webster's definitions of role: "a function or part performed especially in a particular operation or process."