Select the grammatically correct sentence.

A.One of most serious issues with youngsters is an addiction to social media. An issue which needs attention.
B.One of the most serious issues with youngsters is addiction to social media. An issue which needs attention.
C.One of the most serious issues with youngsters is an addiction to social media.
Issue which needs attention.
D.One of the most serious issues with youngsters is an addiction to social media. An issue which needs attention.