instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
The values of strangeness assigned to various particles are based on decay systematics.
answer:
The values of strangeness assigned to various particles are based on what?


question:
Producing sperm and secreting testosterone are the main functions of male reproductive system system.
answer:
Producing sperm and secreting testosterone are the main functions of what system?


question:
Mercury is closest to the sun.
answer:

Which planet is closest to the sun?