Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Input: Consider Input: Induced or spontaneous are the two methods in which mutations arise in dna.

Output: What are the two methods in which mutations arise in dna?

Input: Consider Input: Urea is made in the liver and excreted in urine.

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

Input: Consider Input: Of course, a net external force is needed to cause any acceleration, just as newton proposed in his second law of motion.
Output: Of course, a net external force is needed to cause any acceleration, just as newton proposed in his second law of what?