Question

What is B-DNA,D-DNA,A-DNA,C-DNA?

Answer 1

All these are different forms of DNA depending on how many base pair, vertical rise, rotation are there and how much is the helical diameter.
In B-DNA there are 10 base pair per turn, 3.4 angstroms vertical rise per bp, +36 degrees rotation per bp and 19 angstroms helical diameter.
In A-DNA there are 11 base pair per turn, 2.56 angstroms vertical rise per bp, +33 degrees rotation per bp and 23 angstroms helical diameter.
In Z‑DNA there are 12 base pair per turn, 3.7 angstroms vertical rise per bp, -30 degrees rotation per bp and 18 angstroms helical diameter.