It is the second question,
It creates a shipping lane to and from the Atlantic Ocean and supports a diverse animal population.
Answer:
The main idea is the central, or most important idea in a story, paragraph, or passage
Explanation:
Take "Clowns" for example clowns is the topic. The main idea would be "Clowns are enjoyable for some, scary for others.
1) A
2) D - Not sure 100%
3) - Don't know the song
4) D - Both a and b