Final answer:
Pellagra is the deficiency disease that produces the symptoms known as the "four Ds" - Dermatitis, Diarrhoea, Dementia, and Death.
Step-by-step explanation:
The deficiency disease that produces the symptoms known as the "four Ds" is Pellagra. Pellagra is caused by a deficiency of niacin (vitamin B3) and is characterized by the symptoms of Dermatitis, Diarrhoea, Dementia, and if untreated, Death. These symptoms can include skin rashes, digestive problems, mental confusion, and even death.