Spot the odd one out from the following structures with reference to the male reproductive system:

1. Rete testis

2. Epididymis

3. Vasa efferentia

4. Isthmus 

  (d) Isthmus is the part of female reproductive system. The Fallopian tube (oviduct) in female reproductive system shows four regions, /.e.. infundibulum, ampulla, isthmus and uterine part. Isthmus has a narrow lumen and it joins the uterus. It is the line that demacrates the body of the uterus from the cervix.