BCG vaccine is used to build immunity against-
A. Poliomyelitis
B. Tuberculosis
C. Malaria
D. Whooping cough

Hint: BCG is a vaccine often given to babies and small children where the disease is prevalent. It is a severe infection that affects the lungs, bones, joints, and kidneys, and occasionally other parts of the body.

Complete answer: Option A is incorrect. Poliomyelitis (Polio), is a poliovirus-induced infectious disease. Polio is spread by contaminated water or food, or by contact with the person being infected. It travels from the gut to impact the central nervous system in about 0.5 percent of cases, and there is muscle weakness resulting in flaccid paralysis. Over a few hours to a few days, this can occur. It can cause paralysis and can be easily avoided by a vaccine against polio.
Option B is correct. Bacille Calmette-Guerin (BCG) is a tuberculosis (TB) disease vaccine caused by Mycobacterium tuberculosis infection that is intradermal after birth. TB is a significant infection that affects the lungs, well as the bones, joints and kidneys, and often other areas of the body. For people who have been vaccinated with BCG, the tuberculin skin test (TST) and blood tests to detect infection with TB are not contraindicated.
Option C is incorrect. Malaria is a disease that threatens life. Usually, it is spread by the bite of an infected mosquito called Anopheles. The Plasmodium parasite is borne by infected mosquitoes. Based on the species of plasmodium, the severity of malaria varies. Chills, fever and sweating, which usually occur a few weeks after being bitten, are symptoms. Antimalarial medications may be used to treat it.
Option D is incorrect. A particularly contagious infection of the respiratory tract is Whooping cough (pertussis). In many individuals, it is characterised by a prolonged coughing cough accompanied by a high-pitched breath intake that sounds like "whoop." Whooping cough was considered a childhood illness before the vaccine was developed.

So, the correct answer is Option B.

Note: BCG vaccine should not be administered during pregnancy, nor should it be administered to persons immunosuppressed (e.g. persons infected with HIV) or immunocompromised (e.g. persons eligible for organ transplantation).