Which sentence uses a formal style that is appropriate in an informational piece of writing?

a. athletes should be super careful about what they post since it could keep them from getting into the right university and prevent them from making it in the big leagues.

b. inappropriate posts on social media sites can really foul up a kid's reputation and annihilate friendships, not to mention mess up his whole life.

c. for protection, users should use different passwords for each social media site and e-mail account that requires personal information.

d. don't make up stuff about yourself since it's easy to research your background and find out if what you've posted is a bunch of lies.

C. For protection, users should use different passwords for each social media site and e-mail account that requires personal information.

Explanation:

All other sentences use informal style.

A: in this sentence the phrase super careful is very informal; getting into and big leagues are semi-formal.

B: In this sentence phrases foul up, annihilate friendships, mess up are informal

D: In this sentence phrases  Don't make up stuff, a bunch of lies are informal.

Note: Although sentence C is formal, it lacks clarity.

"For protection, users should use different passwords for each social media site and e-mail account that requires personal information."  Underlined phrase needs clarification.

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