Choose the correct option with respect to the assertion and reason given.
Assertion (A): Not all copulations lead to fertilisation and pregnancy in human beings.
Reason (R): Fertilisation can only occur if the ovum and sperms are transported simultaneously to the ampullary region of the fallopian tube.
The site of fertilisation in human beings is the ampullary region of the fallopian tube. Therefore for fertilisation to take place sperm and ovum have to be transported simultaneously to the ampullary region.
During copulation sperms are transferred into the vagina. From vagina, they reach the ampulla of the fallopian tube passing through the cervix and uterus.
But only one secondary oocyte (ovum) is released during each menstrual cycle (reproductive cycle) which is usually a 28-day cycle.
The secondary oocyte (ovum) is released from the ovary due to the rupture of the Graafian follicle. The secondary oocyte is collected by the fimbriae of the fallopian tube and transported into the ampullary region. Fertilisation and pregnancy is possible if sperm comes in contact with the secondary oocyte during that period.
Hence not all copulations lead to fertilisation and pregnancy.