The correct answer is (d) Nitrate.
Blue baby syndrome, also known as methemoglobinemia, is a condition in which the blood is unable to carry oxygen properly. This can cause the skin and lips to turn blue, and can lead to serious health problems if not treated.
Nitrate is a chemical that can be found in water, soil, and air. It is a natural part of the environment, but it can also be found in fertilizers and sewage. When nitrate is ingested, it can be converted to nitrite in the body. Nitrite can then bind to hemoglobin, the protein in red blood cells that carries oxygen. This can prevent hemoglobin from carrying oxygen, which can lead to blue baby syndrome.
The other options are incorrect because they are not known to cause blue baby syndrome. Phosphate is a mineral that is found in many foods and drinks. Sulphur is an element that is found in many foods and drinks. Arsenic is a metalloid that is found in some rocks and minerals.
Blue baby syndrome is a serious condition that can be fatal. If you think you or your child may have blue baby syndrome, it is important to seek medical attention immediately.