Question

1. tides are affected by

earths gravity alone.
the moons gravity alone.
the suns gravity alone.
the gravity of the moon and the sun.

Explanation:

Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun, and the rotation of Earth. Earth's gravity alone keeps objects on Earth but doesn't cause tides. The Moon has a significant effect due to its proximity, but the Sun also plays a role (especially during spring and neap tides). So it's the combined gravity of the Moon and the Sun.

Answer:

the gravity of the Moon and the Sun.