the true position of the skull uses which of following principles

the true position of the skull uses which of following principles?
1. interpupillary line perpendicular  to the film
2. MSP perpendicular to the film
3. intaorbitomeatal line parallel to the transverse axis of the film
a. 1 only
b. 1 and 2 only
c. 1 and 3 only
d. 1,2 and 3