(B) Spleen

The organ primarily affected by malaria is the spleen. Malaria is a parasitic infection caused by Plasmodium parasites that are transmitted through the bites of infected mosquitoes. The parasites multiply in the liver and then infect red blood cells, leading to symptoms such as fever, chills, and an enlarged spleen. The spleen plays a crucial role in the immune response against malaria, but the infection can cause it to enlarge as it filters out infected red blood cells from the circulation. If left untreated, severe cases of malaria can lead to complications, including damage to the spleen and other organs.

(C) Spinal cord

Vertebrae are part of the spinal column, also known as the backbone or spine. The spinal column is a bony structure that encases and protects the spinal cord, which is a crucial component of the central nervous system. The spinal cord is responsible for transmitting signals between the brain and the rest of the body, allowing for communication and coordination of various bodily functions.

(D) Jonas Salk

The polio vaccine was developed by Dr. Jonas Salk. He and his team conducted extensive research in the 1950s, leading to the development of the inactivated polio vaccine (IPV), which became widely used for the prevention of polio. The vaccine was a significant breakthrough in medical science and played a crucial role in the global effort to eradicate polio.