Which of the following is considered as a marker for epididymal function?

In the epididymis, the columnar cells that, with the basal cells, form the majority of the epithelium. These cells extend from the lumen to the basal lamina, They also have non-motile stereocilia, which are long and branching in the head region and shoer in the tail region. They also secrete carnitine, sialic acid, glycoproteins, and glycerylphosphorylcholine into the lumen.Ref: Ganong&;s review of medical physiology; 24th edition; page no: 419