Dna may be found on the handle or tip of a baseball bat if it is used in a crime.
a. true
b. false

TRUE

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.

It explains why rocks appear in layers