To determine if an invention is obvious in the context of receiving a patent, what do the patent office and court look at?

To determine if an invention is obvious in the context of receiving a patent, what do the patent office and courts look at? The difference between it and existing technologies to see if that difference would be unexpected to someone unskilled in the field at the time of patenting The difference between it and existing technologies to see if that difference would be unexpected to someone skilled in the field at the time of patenting The difference between it and existing technologies to see if that difference would be unexpected to someone skilled in the field at the time of the invention The difference between it and existing technologies to see if that difference would be expected to someone unskilled in the field at the time of the invention