Given a scientific question, generate a correct answer to it.
--------
Question: What is a compound that can form ions when it dissolves in water called?

Answer: electrolyte

Question: What are the two most abundant elements in the universe?

Answer: hydrogen and helium

Question: Respectively, which parts of the circulatory system carry blood from the heart toward capillaries, and return blood to the heart from capillaries?

Answer:
arteries and veins