What phenotype would most likely describe the red cells of a nonsecretor (se/se)?

The correct phenotype that would most likely describe the red cells of a nonsecretor (se/se) is indeed Le(a+b-). This conclusion is rooted in the understanding of the interactions between the Lewis blood group system and the secretor status.

In the Lewis system, two alleles, Le and le, determine the presence of Lewis antigens on red blood cells (RBCs). If an individual is Le(a+b-), this indicates that they produce the Le^a antigen but not the Le^b antigen. Nonsecretors (se/se) do not produce the soluble form of the Lewis antigens in saliva and other secretions. Consequently, individuals who are nonsecretors generally express only the Le^a antigen on their red blood cells due to the lack of the secretor gene necessary to convert Le^a to Le^b.

Individuals who are secretors (Se) can express both Le^a and Le^b (Le(a+b+)) because they can produce the enzymes required to convert Le^a into Le^b. Therefore, those who are Le(a+b-) would not have the Le^b antigen, aligning perfectly with the nonsecretor phenotype.

The combinations explaining the other potential phenotypes show