Which of the Following Statements Concerning Double Covalent Bonds Is

Which of the following statements concerning double covalent bonds is correct?

A) They are found only in molecules that contain P or atoms in the third period or higher.
B) They are only found in molecules that contain large atoms that can effectively overlap with each other.
C) They occur only between atoms containing 2 valence electrons.
D) They always involve the sharing of 4 electrons.