Given a scientific question, generate a correct answer to it.

Example Input: What bifurcates into the right and left bronchi in the lungs?
Example Output: trachea

Example Input: Which organelle is made up of 5 to eight cup shaped, membrane covered stacks of discs known as cisternae?
Example Output: golgi apparatus

Example Input: How many underlying principles does the science of biology have?
Example Output:
four