Root hairs are important to a plant because they increase the surface area for absorption. i really hope this helps.
In order: osmosis, higher, lower
In my experience the head won’t grow back and the rest of the cactus will rot, but in any attempt in saving the plant you can continue to water it as usual or replant the head in a different pot.
The point in which the moon is farthest from the earth is called the apogee.
The moon gets farther and closer to the earth because the moon’s orbit is an ellipse.
