700,000 people are equivalent to the size of Boston's population. The Associated Press reported that due to the highly contagious Delta variant virus, the number of deaths from the new crown in the United States increased from 600,000 to 700,000, and it took only three and a half months.

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; biological;

answer; ( suicide );

answer; preconventional;