'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.
The answer to your question is B
They are both trying to teach you and make you learn
Where is the band playing their concert at?
I don’t know up with how much more I can put.
I liked the company for which I was working for.
When will you arrive at the opening gate?
A preposition is a word that informs you of time or location.
When will you arrive at the opening gate?
The sentence above is the one with the preposition. The word at is the preposition. It answers the question of where you are arriving.
Hope this helped!