TASK DEFINITION: Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
PROBLEM: Urea is made in the liver and excreted in urine.

SOLUTION: What is made in the liver and excreted in urine?

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

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

PROBLEM: The decay rate is measured in a unit called the half-life.

SOLUTION:
The decay rate is measured in a unit called the what?