Concept:An isotherm is a line on a weather map that joins all places having equal temperature at a given time.
Explanation:The term "isotherm" comes from two Greek words: "iso" meaning equal, and "therm" meaning heat or temperature.
So the word literally means equal heat or equal temperature.
On a map, an isotherm is drawn through points that record the same temperature value, and these lines help show how temperature is distributed over an area.
By contrast, lines joining places of equal pressure are called isobars, and lines joining places of equal rainfall are called isohyets.
Therefore, isotherms are specifically connected with temperature, not with rainfall, cloudiness, or pressure.
Answer:D. temperature