Answer:
I do believe your answer is D: Most of Earth's mantle is always moving.
Hopefully this helped! :D
No improvement to this sentence is necessary. It makes perfect sense on its own and sounds right. "Either" always takes an "or" else the word wouldn't make sense, as it's meant to contrast binary options.
eg.
I'm either going to eat food or drink water.
Answer:
Yes, yes it is
Explanation:
I had this for a practice question.
I don’t understand your question
