Open drain system is a breeding place for which of the following?
(a) Flies
(b) Mosquitoes
(c) Organisms which cause diseases
(d) All of these

Correct Answer: (d) All of these

Explanation: Sometimes, drains are opened to dispose off the sewage. These drains can easily get blocked by plastic bags, and can overflow. Therefore, the problems of smell, breeding of mosquitoes, flies and germs are encountered in open drains.