Which Precursor B-Cell Marker Is Used Exclusively in the Work-Up $\varepsilon$

Which precursor B-cell marker is used exclusively in the work-up of acute leukemia in studying B lineage ALL?

A) Mu (µ) heavy chain
B) Epsilon ( $\varepsilon$ ) heavy chain
C) Lambda ( $\lambda$ ) heavy chain
D) Delta ( $\delta$ ) heavy chain
E) None of the above