The correct answer is C. Red ants.
Formic acid is a colorless, pungent liquid that is found in the venom of red ants. It is also produced by some other insects, such as bees and wasps. Formic acid is used as a defense mechanism by these insects. It can cause pain and irritation to humans if it comes into contact with the skin or eyes.
White ants, also known as termites, do not produce formic acid. They are social insects that live in colonies. Termites feed on wood and other plant material. They are considered to be pests because they can cause significant damage to buildings and other structures.
Cockroaches are also social insects that live in colonies. They are found in both urban and rural areas. Cockroaches are considered to be pests because they can contaminate food and spread disease.
Mosquitoes are small, flying insects that feed on blood. They are considered to be pests because they can transmit diseases such as malaria, dengue fever, and yellow fever.
In conclusion, the correct answer is C. Red ants.