Answer:
A. oceanic crust
Step-by-step explanation:
I remember that the ocean is said to cover 71% of the Earth's surface. If you look at a globe, notice that most all the surface is blue like the ocean.
One other note: the surface is the Earth's outermost layer. Think of it this way: surface implies the top of something, something exposed to the outside.
Therefore, the answer is A. Hope this helps you understand the question more! Have a great day, 'kay?