These symptoms can be explained by: "D. Their diets lacked the Vitamin C necessary for collagen tissue formation and repair."
These are the following choices:
A. Their diet lacked enough protein to make collagen.
B. Their diet lacked the Vitamin B6 so necessary to make non-essential amino acids.
C. Their diets lacked Vitamin B1, so they had impaired energy production
D. Their diets lacked the Vitamin C necessary for collagen tissue formation and repair