instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
Negative growth rate results when birth rates fall even lower than death rates.
answer:
What results when birth rates fall even lower than death rates?


question:
The brain is the most complex organ in the human body.
answer:
What is the most complex organ in the human body?


question:
Zero is the net force acting on an object when two equal forces are applied from opposite directions.
answer:

What is the net force acting on an object when two equal forces are applied from opposite directions?