The correct answer is option 4: diphtheria, whooping cough, and tetanus. The DPT vaccine is a combination vaccine given to young babies to protect them from these three diseases.

Diphtheria is a bacterial infection that can cause severe respiratory problems. Whooping cough, also known as pertussis, is a highly contagious respiratory infection that can be fatal in infants. Tetanus is a bacterial infection that affects the nervous system and can cause muscle stiffness and spasms.

Option 1, which includes polio instead of whooping cough, is incorrect. Polio is a separate vaccine given to protect against polio virus. Option 2, which includes pneumonia and tuberculosis, is also incorrect. These diseases are not included in the DPT vaccine. Option 3, which includes smallpox instead of whooping cough, is also incorrect. Smallpox is a separate vaccine and is no longer given.