The correct option is B Uterus of mammals
The endometrium is the inner mucous membrane of the mammalian uterus. It consists of a single layer of columnar epithelium resting on the stroma.
The endometrium is the innermost glandular layer and it is the lining of the uterus, that prevents adhesion between the opposite myometrium. During menstrual cycle, the endometrium grows thick, becomes rich in blood vessels. This represents an optimal environment for implantation of blastocyst.