The correct answer to this question is D, Abstract noun. As the name suggests, an abstract noun is a type of noun. To correctly answer this question, one must know the meaning of a noun. A noun is a person, place, thing, animal, or idea. Barack Obama, hats, and California are all nouns.
A noun becomes abstract when it is something that one of our five senses are unable to detect. A government fits this description because though it is an establishment that we know about, we are unable to detect it with one of our five senses. We can not see, touch, feel, hear, or smell the government.