Answer:
The main idea would be to tell you or teacher what the Bermuda triangle is.
Explanation:
You see that the whole paragraph is talking just about the Bermuda triangle. If something only talks about one thing straight. through the story then that would be the main idea.
Here is the answer that I found for your question :)
The answer should be A because that is those only one that makes sense as we are saying the past tense.