The only movable part of the skull is

A

Upper jaw

B

Lower jaw

C

Both A & B

D

None of the above

The mandible or lower jaw, is the only movable part of the skull, forming the temporomandibular joint with the temporal bone.
The mandible is the largest, strongest and lowest bone in the human face. It forms the lower jaw and holds the lower teeth in place.
So, the correct answer is 'Lower jaw'.