How did watson and crick determine base pairing?

The observed the pairing under a microscope!
hope this helps, Castonmehi! :)

Their model of the DNA molecule showed that the hydrogen bonds could create a nearly perfect fit between nitrogenous bases along the center of the molecule. But the bonds could only form between adenine and thymine, and between cytosine and guanine.So it would be Option D.

please mark brainliest

I think it is A. Cells. Cells pretty much scout your insides and make sure that there are no bacteria in you. I am really good at health