Oil created which were towns that received a great deal of growth in population because of sudden economic growth. a) bank areas b) boomtowns c) large metroplexes d) ship channels

well its not not rising unemployment and falling inflation.

hope this good !

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."