Which of the following sentences is correctly punctuated?
a. the local police asked the f. b.i. to assist with the case.
b. mary remembered to buy milk didn't she?
c. mr. jones visited the ymca before becoming a member.
d. the company held it's annual party at the convention center.

A. The local police asked the F.B.I. to assist with the case.
-F.B.I isn't properly punctuated, as there's a period after 'F.B.I', which implies the sentence ends there.

B. Mary remembered to buy milk didn't she?
-Should be 'Mary remember to buy milk, didn't she?'

C. Mr. Jones visited the YMCA before becoming a member.
-This is correct

D. The company held it's annual party at the convention center.
-It's isnt proper, It's is basically 'it is', The company held it is annual party at the convention center obviously does not make sense.