What types of unemployment will still exist when the economy is at the natural rate of unemployment?

Suppose that to increase sales of hybrid vehicles, auto manufacturers are offering large cash incentives. This is an example of a macroeconomic topic

Indicate whether the statement is true or false

If the cross price elasticity of demand between two commodities is positive, then these commodities are

A) are superior. B) are complements. C) are substitutes. D) are inferior.