In this task, you need to write a topic word from the given fact. The topic word must have at least one word overlap with the given fact. The topic word often involves adding a new word from a related concept. In your topic word, use at least one word from the given fact. Topic words with two or more words work best.

[Q]: Fact: Viruses are so small that they can be seen only with an electron microscope.
[A]: electron microscope lens.


[Q]: Fact: phase changes do not change mass.
[A]: Phase changes.


[Q]: Fact: Precipitation falls on the windward side of the mountain range.
[A]:
Precipitation is snow.