What Was the Most Important Discovery That Watson and Crick

What was the most important discovery that Watson and Crick used to help unravel the way DNA worked?

A) that DNA's base pairs hydrogen bonded with only one other base pair
B) that DNA was a helix
C) that DNA was a double helix
D) that DNA was the genetic material of the cell and it could pass on hereditary information
E) none of the above