How many different nitrogenous bases are found in DNA?

In DNA, there are four different nitrogenous bases that contribute to the genetic code. These bases are adenine (A), thymine (T), cytosine (C), and guanine (G). Each of these bases pairs with a specific counterpart; adenine pairs with thymine, and cytosine pairs with guanine, forming the rungs of the DNA ladder in the double helix structure.

The presence of these four bases allows for a vast array of combinations, which is essential for encoding the information necessary for the development and functioning of living organisms. This four-base system is fundamental to the structure of nucleic acids, distinguishing DNA from RNA, which has uracil in place of thymine and also contains the same bases as DNA minus thymine.

The other numbers provided in the choices do not accurately reflect the total count of nitrogenous bases found in DNA, as only these four are present in its structure.