Answer : Option D) Strenuous exercise has caused her body to be in oxygen debt, and she is breathing hard while lactate is transported to the liver. This is a result of anaerobic respiration.
Explanation :
Frida was breathing normally while doing the exercise, but when she stopped there was a sudden decrease of oxygen in her body which demanded more oxygen to be breathed in. This strenuous exercise also allowed her lungs to breathe more oxygen which resulted into breathing hard as lactate was being transported to the liver, which was eventually the result of anaerobic respiration.