The post-surgery complications of a kidney transplant like infection and sepsis is caused due to the use of

The correct option is B Immunosuppressant.
Immuno-suppressant drugs are prescribed if a patient is suffering from an autoimmune disorder or has undergone an organ transplant like a liver, heart or kidney. This is done to prevent the organ from being damaged by the immune system of the recipient. However, as the immune system is being suppressed the patient/recipient may be prone to infections, sepsis or other pathological conditions.

So, the correct answer is 'Immunosuppressant'