Which shows a correctly paired dna molecule? a. tag ta gta at b. tag ta atg cc c. tct ta atg at d. tag ta atc at

The correct option is D.
The DNA molecule is made up of four different bases, two of which are purines and two are pyrimidines. These four bases have a way of associating with one another. The bases are: Thymine [T], Adenine [A], Cytosine [C] and Guanine [G]. Thymine only associate with Adenine, thus forming AT, while guanine only associate with cytosine forming GC.
Looking at the pairs given above, you will notice that it is only in option D that these bases are correctly arranged, that is, TA, AT, GC, TA and AT. When checking, look at the alphabet above and then the one that is below it.

D would be the correct answer I believe.

The right answer is b hydrogen bonds!