Choices B) and C) can be eliminated as options because they reference income. Income is exactly as it sounds. It is incoming money or money being paid. Conversely, expenses are the moneys being spent.
Choice A) is eliminated due to the word essential. Essential is something that would be required. Examples of essential expenses would be things such as groceries, rent, medication and so on. That then leaves the only correct option to be choice D) non-essential expenses.
Answer: Martin Luther King in this passage means that he wants his kids/everyone to be judged by what their personality is like and not their skin color.