The correct option is C Methemoglobin
A blue baby syndrome is caused by methemoglobinemia. It is caused by nitrate contamination in groundwater resulting in decreased oxygen carrying capacity of haemoglobin in babies leading to death. It begins when large amounts of nitrates in water are ingested by an infant and converted to nitrite by the digestive system. The nitrite then reacts with oxyhaemoglobin to form methemoglobin, which cannot carry oxygen.