Since Russell's Wife Died, He Has Been Eating the Exact

Since Russell's wife died, he has been eating the exact same thing-and a very small amount of it-for breakfast and lunch every day. Most nights, he skips dinner. Sometimes he seems confused when his granddaughter calls to check in on him. Based solely on this information, which diagnosis is most likely?

A) Malnutrition is causing symptoms that mimic dementia.
B) He must have had a ministroke.
C) He is likely in the early stages of Alzheimer disease.
D) Lewy body dementia is the most likely cause of his symptoms.