A. Your heart starts beating fast and you get very nervous when the news reports that your house is in the path of the tornado.
B. Your parents call you to ask why your seven-year-old brother is not home yet and you realize you forgot to pick him up from school.
C. You are extremely nervous and start sweating while waiting in line for your name to be called to accept your high school diploma.
D. You begin shivering while hiding in the bathroom of the grocery store hoping a robber does not realize you are there.
I think it's A, since eustress is stress benefiting the person. When your heart starts beating fast, more blood is pumped to the brain(?), so I guess it benefits somehow. I'm sorry if i sound confusing!