There are different bases of DNA​

4

Explanation:

Because there are four naturally occurring nitrogenous bases, there are four different types of DNA nucleotides: adenine (A), thymine (T), guanine (G), and cytosine (C).

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.