pH is 7.2; PCO2 12; PO2 55 most likely cause is -
In this patient
pH → Decreased (Normal 7.4)
PCO2 → Decreased.
First step

Determine whether it is acidosis or alkalosis.
The decrease in pH suggests acidosis.

Second step

Observed HCO3-/PCO2 to determine the cause of acidosis or alkalosis
Only one value is mentioned and that too is not in sync with the pH
PCO2 value of 12 indicates respiratory alkalosis
But the pH of the serum indicates acidosis, this suggests the presence of some other disorder besides the respiratory alkalosis which must be producing acidosis
Option 'a' appears to be appropriate because the coexisting metabolic acidosis will cause a decrease in pH.
Metabolic acidosis and respiratory alkalosis
Metabolic alkalosis
Respiratory acidosis
Respiratory alkalosis