Which of the Following Plays a Part in the Increase $\mathrm { pO } _ { 2 }$

Which of the following plays a part in the increase in ventilation with moderate exercise?
A. Reflexes from moving limbs
B. Decrease in body temperature
C. Fall in arterial $\mathrm { pO } _ { 2 }$
D. Rise in arterial $\mathrm { pCO } _ { 2 }$