You didn't italicize any words, so I will just try to explain the figures of speech you have listed above, and hopefully that will help you.
1. hyperbole - this is exaggeration. For example, 'I waited for him for a hundred years' to denote you had to wait for someone for a longer period of time. You didn't really wait for him for a hundred years - it is an exaggeration. Poets and writers often use this figure of speech in order to make a statement, and impact on the reader. I can't see examples of hyperbole in this excerpt, so I wouldn't choose that as the correct option here.
2. paradox - paradox is a figure of speech in which you combine two things which are opposite from each other in nature. It creates an absurd phrase because two contradictory statements are brought together, such as 'drinking a lot of water can make you thirsty.' I can see an example of paradox in the excerpt above, which is "day brought back my night." Day and night are each other's opposites, which makes a paradox if they are brought together like this.
3. understatement - this is a figure of speech which authors use when they want to make something appear to have a lesser value than it actually has; when they want to demean something as being less important that what it seems. An example of an understatement would be the following - you get a lot of money at a lottery, and when asked how you feel about it, you say 'I'm happy.' You would obviously feel much stronger emotions if this happened. I don't see instances of understatement here either.
I would choose paradox as the correct answer here.
the excerpt is "They died—nor were those flowers more gay, the flowers that did in Eden bloom"
ans are:
The flower is doomed, just like the Garden of Eden.
Paradise is all around us if we just take the time to notice it.
