Q1. The chemical name for urea is
(a) Aneurin
(b) Chloroethene
(c) Carbamide
(d) None of these
(UPSC Prelims 1987)
Answer: (c) Carbamide
Explanation: Urea, a nitrogen-rich compound used in fertilizers, is chemically known as carbamide. It is synthesized from ammonia and carbon dioxide, and plays a key role in agriculture and medicine.
Q2. Azolla gives a good biofertilizer when mixed with
(a) Blue-green algae
(b) Cow dung
(c) Bone-meal
(d) Urea
(UPSC Prelims 1987)
Answer: (a) Blue-green algae
Explanation: Azolla, when combined with blue-green algae (cyanobacteria), forms an effective biofertilizer, especially for paddy fields. This mixture enhances nitrogen fixation, improving soil fertility naturally.
Q3. Why DDT is banned in western countries ?
(a) It remains in environment for a long time
(b) The insects are immunised
(c) It is a highly poisonous insecticide
(d) None of the above
(UPSC Prelims 1987)
Answer: (a) It remains in environment for a long time
Explanation: DDT (Dichlorodiphenyltrichloroethane) is banned due to its persistence in the environment, leading to bioaccumulation and ecological harm. It affects wildlife and human health, despite its effectiveness as an insecticide.