I believe it is the third option but it could be the fourth.
Because a beach is not a person, the only pronoun that can be used is "it."
can you explain this question a little bit more?
'Exert' means to apply force on influence over something else, this can be in a negative or positive way. In this quotation, it means that language, if used correctly, has the ability to express a 'hidden power'. It's also worth mentioning that the simile is relevant as the moon has an influence on the level of tides on Earth.
C. It demonstrates how miserable she felt.
Zitkala-Sa was put through many tortures, based on this excerpt. It is clear that she was taken away from her mother young, and that her captors did terrible things to her like tie her to a chair and cut off one of her braids. If she was treated like this, it serves as an example for how the rest of her people were probably also treated.