question:
What is the main function of the circulatory system?

answer:
transport materials

question:
Which activity is an example of a chemical change?

answer:
burning wood to produce ashes

question:
Tigers and household cats are members of the same family; however, their sizes are vastly different. What is the cause of this difference?

answer:
genetics

question:
In which oceanic zone do clams and crabs survive by burrowing in the sand?

answer:

intertidal