Art is considered many things...… from music to paintings. This is what everyone knows art as. But really art is what you end up with when your struck with an amazing idea or you see things from a different perspective and notice that it makes something else. The reason why the question "what is art" cannot be answered is because we don't really know what art is ourselves, our definition of art expands everyday when something new is noticed. I'm only in high school so maybe my answer is stupid and doesn't really help..... or maybe it will help. But seeing that no one else has answered your question, I thought I'd give my opinion. Hope this helps a little :)
First off you got a., b., c., d. in the wrong places but the answer is sarcophagus
The answer is Constructed of Huge stones!
Have a wonderful day!