A 20yo man has a head on collision in a car

A 20yo man has a head on collision in a car. On presentation he is breathless, has chest pain and
fx of 5-7th rib. CXR confirms this. What is the most appropriate initial action in this pt?
a. Antibiotics
b. Analgesia
c. O2 by mask
d. Physiotherapy
e. Refer to surgeon

Ans. The key is C. O2 by mask. [There was debate in this forum that pain relief should be given first which will automatically relieve breathing problem. But others told O2 first]. O2 first is the correct answer!