Consider the following statement: When jumping from some height,you should bend your knees as you come to rest,instead of keeping your legs stiff. Which of the following relations can be useful in explaining the statement?

• A
  $\Delta \overrightarrow{P_1} = - \Delta \overrightarrow{P_2}$
• B
  $\Delta E = - \Delta (PE + KE) = 0$
• C
  $\overrightarrow{F} \Delta t = m \Delta \overrightarrow{v}$
• D
  $\Delta \overrightarrow{x} \propto \Delta \overrightarrow{F}$