Answer:
A. The narrator's efforts had no effect on Usher.
Step-by-step explanation:
Now the reason why Choice A is correct can be seen in this passage in the story:
"...and during this period I was busied in earnest endeavors to alleviate the melancholy of my friend. By painting and reading simultaneously, or as I listened in a trance, I witnessed his madcap guitar solos. As a closer and closer intimacy admitted me more unreservedly into the recesses of his spirit, the more bitterly I perceived the futility of any attempt to cheer a mind from which darkness, as if an inherent positive quality, poured forth upon all objects of the moral and physical universe in one unceasing radiation of gloom."
where the narrator states that his efforts were all futile (meaning useless and of no effect) towards cheering up Usher.