Which of the following statements best describes dna?
a. dna are the same as genes.
b. all living things contain dna.
c. there are three bases that compose dna.
d. billions of people in the world have the same genetic code.

B. All living things contain DNA. 

The four bases in DNA are adenine, cytosine, guanine, and thymine.

These four are divided into two groups. The pyrimidines, the single-ring nitrogenous bases, is where thymine and cytosine is included. The purines, the double-ring nitrogenous bases, includes adenine and guanine. 

Cytosine will only bond with guanine; they form three hydrogen bonds. Adenine will only bond with thymine forming two hydrogen bonds.

Balkan nationalism increased tensions between austria and russia