instruction:
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.
question:
Fact: unequal heating of Earth 's surface by the Sun causes global wind patterns.
answer:
earth our planet.


question:
Fact: Caffeine is a central nervous system stimulant.
answer:
caffeine coffee.


question:
Fact: a stopwatch is used to measure time.
answer:

Measuring time.