Carrie has been sad a lot lately. she is down on herself, has very little appetite, can't sleep, and doesn't want to be around her friends or family. carrie's condition is most likely

Depression

Explanation:

Depression is the overwhelming sensation of sadness that causes physical symptoms and it can interfere with normal life. Some of the symptoms of depression are loss of interest in activities that were pleasurable, appetite loss, difficulty to concentrate, insomnia, feelings of emptiness and guilt.

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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."