Answer:
adenine (A), thymine (T), guanine (G) and cytosine (C). The order, or sequence, of these bases determines what biological instructions are contained in a strand of DNA
Explanation:
DNA has three types of chemical component: phosphate, a sugar called deoxyribose, and four nitrogenous bases—adenine, guanine, cytosine, and thymine.
stethoscope is the instrument used to measure heart beat
a is the answer
