The sea that separates Indonesia from Australia is the Arafura sea.
The correct answer is D. ocean floor mapping and earthquake tracking
Tracking earthquakes is helpful because it shows where it came from and what caused it, as well as how it affected the environment, while ocean floor mapping is useful because it shows how the bottom of the sea changed over time which happens due to tectonic activity.
The earth isn't getting bigger even though the continents are spreading apart is because the continents are simply being shifted from one location to another, but no land or mass is being created. The mass of certain parts of the world is simply being displaced from one location on the earth to another or its shape is simply being changed by being pushed up or below the earth's surface.
I would say a. granite maybe. i am not sure.