[poll id=”199″]
ANSWER:
B. 30%
Guanine pairs up with Cytosine. So if 20% of the DNA stand is Guanine, it means 20% of it is Cytosine. Thus, the 60% left is made up of Adenine and Thymine. Since Adenine pairs up with Thymine, it must be evenly split into 30:30. Thus, 30% is composed of Thymine.