The european union created a single monetary unit to replace the national currencies of twelve member nations. this common currency is known as the:

Euro.

Explanation:

An international organization of European countries formed to protect the economic and social policies to strengthen peace in Europe, named European Union. It ensured the European integration by adopting a common currency (Euro), unified foreign policy, common citizenship rights and to protect Europe from any external threat.

i believe

clean air is essential for health and survival

clean air provides nitrogen gas for plant respiration

clean air supplies oxygen that enables living organisms to breathe

hope this

i am brianly

sorry if this doesn't

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."