Aleontologists have discovered a lot about animals, like dinosaurs and trilobites, that lived long ago. How do paleontologists learn how the animals of the ancient past looked and acted?

They study weather patterns of the past.

They study photographs.

They study fossils.

They study the fish of today.

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."

answer; environmental science;