Which of the Following Is NOT a Constitutionally Permissible Limitation

Which of the following is NOT a constitutionally permissible limitation on the Second Amendment right to bear arms?

A) Background checks for gun buyers
B) Mandatory trigger locks
C) Prohibitions on concealed weapons
D) Limits on the possession of firearms by the mentally ill and by felons
E) Restrictions on dangerous and unusual weapons not typically used for self-defense