The correct answer is: A.
Shorter.A double bond is shorter than a single bond because the two atoms in a double bond are held together by two pairs of electrons, while the two atoms in a single bond are held together by only one pair of electrons. This means that the electrons in a double bond are shared more strongly between the two atoms, which makes the bond shorter.
Option B is incorrect because a double bond is not longer than a single bond. Option C is incorrect because a double bond is not the same length as a single bond. Option D is incorrect because the answer is not none of the above.