The Dimensions of Our Galaxy Are Not Precisely Known

The dimensions of our galaxy are not precisely known. For example, our distance to the galactic center is known only to 8 ± 1 kpc. One fundamental reason for this lack of further knowledge is that:

A) the Milky Way Galaxy is an irregular galaxy without much uniformity.
B) the whole system rotates rapidly, making measurements difficult.
C) our detection systems are not powerful enough to see across the entire galaxy.
D) we are inside the galaxy.