I would go with the answer E). Just because slavery ended years ago doesn't mean that's its still over even to this day, it use to be about gender as well back than where women couldn't vote but no one cares about that today, the things people care about is race because as the famous quote someone said, humans hate what they don't understand, so most races don't understand why people are all different, so they want to hate them since they don't understand and also get higher authority as well, but to get back to topic race is the most common thing today that encourages people to leave and migrate cause they might not feel welcome.
D. That something is so different from anything else that its unique.
Explanation:
A metaphor is a figure of speech in which a word or phrase is applied to an object or action to which it is not literally applicable. So D is just the only one that makes sense.
