State the conditions under which nitrogen gas can be liquefied.

Gases can be liquefied by applying high pressure. As gases are highly compressible, on applying high pressure, the molecules of a gas would come close, inter molecular forces would increase and it will condense into a liquid. By lowering the temperature:Gases can be converted into liquids by simple cooling.

in cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. a contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

explanation: