Some T Cells Express $\gamma$ $\delta$ T-Cell Receptors Rather Than $\alpha$ $\beta$

Multiple Choice

Some T cells express $\gamma$ : $\delta$ T-cell receptors rather than $\alpha$ : $\beta$ T-cell receptors. The organization of the $\alpha$ locus and the $\delta$ locus helps to ensure that each T cell cannot express both types of T-cell receptors. The mechanism involved is that:

A) The rearrangement of a T-cell receptor $\alpha$ gene deletes the $\delta$ locus on that allele.
B) The rearrangement of a T-cell receptor $\delta$ gene deletes the $\alpha$ locus on that allele.
C) The RAG recombinase enzymes are down-regulated immediately after the first T-cell receptor genes rearrange.
D) The $\alpha$ : $\beta$ T-cell receptor signals the T cell to delete the $\delta$ locus.
E) The $\gamma$ : $\delta$ T-cell receptor signals the T cell to delete the $\alpha$ locus.