The correct answer is A. At high latitudes.
The “land of the midnight sun” is a region where the sun does not set below the horizon at least one day per year. This phenomenon occurs in places north of the Arctic Circle and south of the Antarctic Circle. The further north or south you go, the longer the period of time that the sun is visible at night.
At middle latitudes, the sun does set below the horizon at night, but it does so for a shorter period of time than at high latitudes. Near the equator, the sun does not set below the horizon at all during the summer months. In the desert southwest and on the West Coast, the sun does set below the horizon at night, but it does so for a shorter period of time than in other parts of the United States.