I think that the best phrase to fit into the blank is a "scientific theory".
A scientific theory is developed through experiments which use the scientific method, and a theory can be improved if additional data is available or if people provide suggestions which make the theory fit the data better.
Answer:
The answer is aabb (Cremello).
Fruit flies produce offspring relatively fast and have specific traits, such as eye color and body color/shape. They are easy to observe and their traits are easily traced throughout the next generations.
There are radio waves, microwaves and infrared waves
