Answer: Abby's dog is definitely suffering from a DEFICIENCY type of disease.
Therefore, option (D) is correct.
Explanation: Vitamin D is quite an important nutrient that is essential to our health in boosting our immunity levels, strengthening our bones, enhancing cell growth and most importantly, helping create new hair follicles
Symptoms, such as hair loss and slow growth can occur when living organisms lacks the recommended amounts of vitamin D.
Low levels of Vitamin D has been linked to alopecia, also known as spot baldness, bone softening, low bone density, osteoarthritis, heart disease, and cancer.