He recently underwent right hip replacement and had taken heparin to prevent thromboembolic complications

A 64 year old man arrives to the emergency room after recurrent vomiting of blood for the last 2 hours. He recently underwent right hip replacement and had taken heparin to prevent thromboembolic complications. Internal bleeding is suspected and treatment with protamine has begun.
What kind of antagonism is related to this treatment?
A- Chemical
B- Competitive
C-Irreversible
D-Physiological
Answer: https://goo.gl/9ZvPkW