A. Immunity means the ability of a body to recognize, destroy and eliminate external disease causing agents.
B. Vaccination helps a person to acquire immunity against a certain disease.
C. The vaccine is a solution containing the disease-causing organisms in a diluted or weakened form.
D. The commonly used vaccine are DPT, BCG, hepatitis vaccine, polio vaccine, typhoid vaccine etc.
Select the correct statement.

The correct option is D All of the above
The immune system is a body's defense mechanism that protects against disease. To function properly, an immune system must detect a wide variety of agents, known as pathogens, from viruses to parasitic worms and distinguish them from the organism's own healthy tissue. Vaccines that contains weakened or dead bacteria or viruses reduce the risk of infection by working with the body's natural defenses to help it safely develop immunity to a disease by producing antibodies. When germs, such as bacteria or viruses, invade the body, they attack and multiply. This invasion is called an infection. The immune system then has to fight the infection. Once it fights off the infection, the body is left with a supply of cells that help recognize and fight that disease in the future. The most common vaccines are DTP, hepatitis vaccine, polio vaccine, typhoid vaccine, BCG etc. Thus, the correct answer is option D.