A Patient's Total IgG Is in the Normal Range,but He

A patient's total IgG is in the normal range,but he suffers from recurrent infections with encapsulated bacteria such as Streptococcus pneumoniae and Haemophilus influenza.T-cell functions are all normal.What is the most likely cause of the infections?

A) Tyrosine kinase deficiency
B) Common variable immunodeficiency
C) IgG subclass deficiency
D) Selective IgA deficiency