Write a correct answer to the given question based on its associated fact. Make sure that your answer is contained in the associated fact. Don't be creative and introduce any new word that is not mentioned in the associated fact! Remember that the associated fact has been rearranged to form the question. So, the correct answer words must lie within the associated fact. The correct answer can be a word, phrase, or even a sentence.

Fact: rain falls on the windward side of the mountain range. 
Question: What falls on the windward side of the mountain range?
rain.

Fact: Plants exhibit phototropism, or growing toward the sun or artificial light. 
Question: What is called when plants grow toward the sun or an artificial light?
phototropism.

Fact: differentiation is the process by which unspecialized building blocks of organisms become specialized. 
Question: what goes from unspecialized to specialized during differentiation?

building blocks of organisms.