Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
--------
Question: The cardiovascular system in the human body consists of the heart, a network of blood vessels, and blood.

Answer: Which system in the human body consists of the heart, a network of blood vessels, and blood?


Question: Compression zones is the opposite of rarefaction zones, where air molecules in waves are loosely packed.

Answer: What is the opposite of rarefaction zones, where air molecules in waves are loosely packed?


Question: Radioactive nuclei and particles are represented by nuclear symbols.

Answer:
Radioactive nuclei and particles are represented by which symbols?