You are presented with the question "What mostly contain the instructions for a single protein?" and the following answer choices: 
- resistance activities
 - Veins and arteries.
 - A Greek letter
 - sensory neurons
 - fur seals
 - parasites
 - units of heredity
 - colors of the spectrum

Now knowing that most genes contain the instructions for a single protein and genes are the basic unit of heredity, choose the best answer.


 

       units of heredity  