Test: Sexual Reproduction In Humans

The zona pellucida layer of the ovum shows certain changes after the penetration of sperm and thus checks the entry of additional sperms. 

The sperm produced in testis and travel through Vas deferns to come out through urethra, so we block vas deferns to prevent the flow of sperm.

After every 28-30 days a mature ovum is released by ovary and wait for sperm to get fertilized. In case the fertilization does not takes place the uterine wall breaks and ovum comes out of vagina as blood. It is known as menstruation.

The fetus is connected to the placenta through the umbilical cord, a tube that contains two arteries and a vein. Blood from the fetus enters the placenta through the umbilical arteries, exchange gases and other substances with the mother's blood, and travels back to the fetus through the umbilical vein.

Correct Answer :- c

Explanation : Almost all organs are completely formed by about 10 weeks after fertilization (which equals 12 weeks of pregnancy). The exceptions are the brain and spinal cord, which continue to form and develop throughout pregnancy. Most malformations (birth defects) occur during the period when organs are forming.