Factor-Intensity Reversal explains the situation in which a commodity is the labor-intensive commodity in the labor-abundant country and the capital intensive commodity in the capitalabundant country.  The Factor-Intensity Reversal rests on the elasticity of substitution of factors of production. Elasticity of substitution of factors of production measures the ease with which one factor of production can be substituted for another within the production as the relative price of the factor declines. The correct answer is " A ".