In which one of the following sentences is the apostrophe used correctly?

a. the train began it's journey across country.
b. i put the letter back into it's file.
c. it's up to you to decide what to do.
d. the cat licked it's paws while the dog watched.

The answer is C, because "it's" is "it is", so it would make sense if you said, "it is up to you to decide what to do"

In my honest opinion , i’d say franklin d roosevelt was a president that impacted our nation , i say this because fdr is voted among top three best us presidents and he was the longest serving president by 3 terms , usually presidents only supposed to have two terms increments of 4 years , equivalent to 8 years total before election time. and he established the fdic , through the 1933 banking act and he established the us , social security system , during his presidency, and established a national minimum wage , through the fair labor standards act , fdr led the allied coalition to victory in wwii and he played a major role in the creation of the united nations.