The Comparison of Two Bullets Is Possible with the Comparison

The comparison of two bullets is possible with the comparison microscope.Such a study is made difficult by the fact that:

A) Lands and grooves are subject to wear and tear and hence striations markings are susceptible to continuing change.
B) Often evidence bullets are distorted on impact and only small areas are found with intact markings.
C) The presence of grit and rust can to some degree alter the markings on bullets fired through the same barrel.
D) All of the above