For a system to be closed under an operation, and when any two elements in the system are combined using the operation, the result must still be an element of that system. For instance, when any two natural numbers (1, 2, 3, . . .), are added together, the result will always be a natural number. When answering the following questions, consider the system of all polynomial equations and the system of all rational equations.

Part A
Which systems are closed under addition? If either system is not closed under addition, provide a counterexample
Part B
Which systems are closed under subtraction? If either system is not closed under subtraction, provide a counterexample.
Part C
Which systems are closed under multiplication? If either system is not closed under multiplication, provide a counterexample.
Part D
Which systems are closed under division? If either system is not closed under division, provide a counterexample.
Part E
Based on which operations the system of polynomial equations is closed under, which system of numbers is most similar to the system of polynomial equations? Explain your answer, and provide any needed counterexamples.
Part F
Based on which operations the system of rational equations is closed under, which system of numbers is most similar to the system of rational equations? Explain your answer, and provide any needed counterexample