Why two ingredients are necessary in order for a substance to be called a hand cream

lanolin  and a mixture of stearic acid and triethanolamine

Explanation:

lanolin -

It is responsible for the absorption of the water in the skin , i.e. , to make the skin hydrated .

Lanolin is ester of the long chain fatty acid , with waxy feel to it .

The mixture of stearic acid and triethanolamine  act as a emulsifying agent .

These reactants reacts to give salt , hence act as an emulsifying agent .  

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:

10 years is the answer