Creative and easy to start out with and sometimes it can be very hard to figure out
I believe the answer is d) Unity. Since unity is what makes all elements in an artwork combine together well-harmoniously, I would think that'd be the most significant principle of a design according to photography.
A harpsichord is a keyboard instrument similar to a piano but the notes are usually higher in pitch. The rest of it, I'm sorry to say, I don't know. I was never taught any of that.
