The structure of DNA as a double helix with complimentary strands was a major breakthrough in our understanding of biology. The major contributions to the discovery of the DNA double helix structure, (although not all were recognized by the Nobel prize Committee) were made by:

Erwin Chargaff and Franklin Rosalind

Explanation:

Erwin chargaff's work on base composition studies which involves the compilation of the four nitrogenous bases in the DNA double helix

Franklin Rosalind and Maurice studies on Xray diffraction images of DNA studies also assisted in the determination of the position and the distances.

the answer is b.) hydrogen bonds between bases.

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