What Evidence Suggests That a Biological Function Exists for Z-DNA $\alpha$

Multiple Choice

What evidence suggests that a biological function exists for Z-DNA?

A) Z-DNA is unique because it is made up of alternating pyrimidine and purine residues in the anti and syn conformation.
B) The left-handed nature of Z-DNA allows phosphate separation which is stabilizing..
C) X-ray structure of the protein Z $\alpha$ binding Z-DNA has been identified.
D) A and B
E) A,B,and C