Why was the aboriginal culture isolated for thousands of years? O Australia is an island/continent
O Aboriginals forced other cultures out
O Australians refused to allow foreigners in
O Australians prevented outside trade

The first.

Explanation:

On account of how isolated Australia is from the rest of the world geographically, it might have made it harder for them to interact with other group of people. This is similar to how The Americas were seemingly relatively unknown because there had been an ocean away and didn't seemingly connect to any of Europe, Asia, or Africa.

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; the candidate for vice president;