When $$\frac{{\vartriangle {{\text{X}}_1}}}{{\vartriangle {{\text{X}}_2}}} > \frac{{{\text{P}}{{\text{X}}_2}}}{{{\text{P}}{{\text{X}}_1}}}$$   then we can

A. Do nothing

B. Go to substituting of $${{{\text{X}}_1}}$$ to $${{{\text{X}}_2}}$$

C. Employ any combinating of $${{{\text{X}}_1}}$$ and $${{{\text{X}}_2}}$$

D. Employ only $${{{\text{X}}_2}}$$

Answer: Option C