Hello, again @Abhisar

5. In mammals the ribcage is reduced, protecting the heart and lungs but not the intestines. This
has occurred as a result of
a) The need to minimise weight for rapid locomotion
b) Change in diet which has allowed the digestive tract to be shorter
c) Birth of large, highly-developed young
d) Change to a parasaggital (improved) gait

I would say b?

Question

Hello, again @Abhisar 

5. In mammals the ribcage is reduced, protecting the heart and lungs but not the intestines. This 
has occurred as a result of
a) The need to minimise weight for rapid locomotion
b) Change in diet which has allowed the digestive tract to be shorter
c) Birth of large, highly-developed young
d) Change to a parasaggital (improved) gait

I would say b?