What scientist determine the rule that A always pairs with T and C alway pairs with G

Explanation:

These base pair relationships are often called Chargaff's rules of DNA base pairing, named after the Columbia University scientists who observed that there are equal molar concentration of A & T, as well as G & C in most DNA molecules.

Erwin Chargaff

Explanation:

Erwin Chargaff found that in DNA, the ratios of adenine (A) to thymine (T) and guanine (G) to cytosine (C) are equal.

(dnalc.cshl.edu)

i believe it is c: genes for body color and wing size are inherited separately from each parent.