Which of the Following Is NOT an Example of a Checkpoint

Multiple Choice

Which of the following is NOT an example of a checkpoint in lymphocyte maturation that contributes to the selective maturation of cells with useful antigen receptors?

A) B cell precursors that cannot express Ig g heavy chains die by apoptosis.
B) T cell precursors that cannot express TCR b chains die by apoptosis.
C) Immature B cells that bind to self antigen with high affinity die by apoptosis.
D) Developing T cells that fail to express TCR a chains die by apoptosis.
E) Developing T cells that recognize self major histocompatibility complex (MHC) molecules with high affinity die by apoptosis.