What is the defining feature of a progressive tax?
a. a progressive tax is collected monthly, rather than yearly.
b. a progressive tax is collected every year, rather than just once.
c. under a progressive tax, taxpayers have a more direct say in how their money is used.
d. under a progressive tax, those with more income shoulder more of the tax burden.

i dont know sorry why dont you looking it up on google

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."