Which of the following properties of acquired immunity is the basis of vaccination?

Explanation

Functions of the part labelled 2, i.e., placenta, are as follows: 1. Placenta aids in all vital metabolic functions of the foetus. It is the means of supplying nutrients to the foetus from the mother. It also helps in exchange of respiratory gases and excretion of nitrogenous wastes from the body of foetus. 2. Placenta also acts as an important endocrine gland that secretes a number of hormones. 3. Placenta acts as a barrier preventing the entry of pathogens and toxins in the body of foetus. 4. Placenta is permeable to antibodies from mother which enter the foetal blood and provide protection against diseases. 5. Placenta stores fat and glycogen which can be broken down and absorbed by the foetal part of placenta.