How has the building of dams created problems for countries rivers in southwest asia. dams are too expensive to build to be practical. dams limit the water available to countries further downstream. few countries have the technology needed to be able to build dams. countries in sw asia are not allowed to build dams along shared rivers.

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."