A person preparing food like Mary Mallon can be a major source of spread of disease:

The correct option is D Typhoid
A person preparing food like Mary Mallon can be a major source of spread of disease typhoid. The most notorious carrier of typhoid fever was Mary Mallon, also known as Typhoid Mary. She became the first asymptomatic carrier to be identified by this disease. She was a cook who spread this disease to many people associated with her.
So, the correct answer is Typhoid.