Answer is B (Pneumocystis carinii pneumonia) : Pneumocystis carinii infections are associated with deficient cell mediated immunity and not with humoral immunodeficiency. Humoral immunodeficiencies i.e. predominantly antibody deficiencies are associated with recurrent serious infections with pyogenic bacteria and giardiasis. Recurrent sinusitis and recurrent subcutaneous abscess result from infection with pyogenic bacteria and hence are consistent with diagnosis of humoral immunodeficiency.