After a sperm has penetrated an ovum in the process of fertilization, entry of further sperms is prevented by

The eggs of elephant are

Assertion : Old age is not an illness. It is a continuation of life with decreasing capacity for adaptation.

Reason : Cessation of mitosis is a normal genetically programmed event.

The placenta of human beings belong to the category of

Atretic follicles are found in the