The correct option is D Methaemoglobin
Blue baby syndrome
Higher nitrate levels cause a blood disorder in infants of 6 months. This disorder is called blue baby syndrome. The nitrates get converted to nitrites in the body which then bind to the haemoglobin.
The methemoglobin thus formed will be unable to carry oxygen resulting in the skin of the baby turning blue. This is called blue baby syndrome.
Final answer
(D) Methaemoglobin