If a Double-Negative Thymocyte Has Just Completed a Productive β-Chain

If a double-negative thymocyte has just completed a productive β-chain gene rearrangement,which of the following describes the immediate next step in the development of this thymocyte?

A) A pre-T-cell receptor is assembled as a superdimer.
B) Rearrangement of γ- and δ-chain genes commences.
C) Expression levels of RAG-1 and RAG-2 are elevated.
D) The linked δ-chain genes are eliminated.
E) This cell will inevitably differentiate into a committed γ:δ T cell.