Once Infected with Trypanosoma Brucei, the Patient's Immune System Cannot

Once infected with Trypanosoma brucei, the patient's immune system cannot clear the infection and develop immunity because the parasite

A) has flagella that allow it to travel all over the body.
B) changes its glycoprotein surface antigens every time it replicates.
C) matures into infectious trypomastigotes.
D) invades the central nervous system.
E) reproduces by binary fission.