Indicate which of the following statements is true (T) or false (F).

Indicate which of the following statements is true (T) or false (F).
 
  a. __ Immature T cells failing to successfully recombine a -chain locus die by apoptosis.
  b. __ Apoptotic T cells are ingested by medullary epithelial cells.
  c. __ Allelic exclusion of the T-cell receptor  and  chains is effective; therefore, all T cells express only one T-cell receptor on the cell surface.
  d. __ T-cell receptor rearrangements have many features in common with immunoglobulin rearrangement, including the use of the RAG-1 and RAG-2 genes.
  e. __ The expression of the pre-T-cell receptor is required in order to halt -, -, and -chain rearrangements.