Fact 1: The gravitational pull of the Moon on Earth 's oceans causes the tides. Fact 2: Planetary moons are natural satellites. Given the two facts above, the pull of what on the Earth's oceans cause the tides?

pick from the following.
(I). A yellow star;
(II). Time and energy;
(III). energy of moving objects;
(IV). A natural satellite;
(V). flow of electrons;
(VI). An artificial satellite;
(VII). A red star;
(VIII). hydrogen and oxygen;
Answer:
(IV).