2021 GS Paper I, all questions
UPSC Prelims 2021 · GS Paper I
Question 21: Environment and Ecology
Which one of the following is used in preparing a natural mosquito repellent?
aCongress grass
bElephant grass
cLemongrass
dNut grass
AnswerUPSC’s answer is (c).
Lemongrass (and the closely related citronella grass) yields an aromatic oil rich in citral and citronellal, which repels mosquitoes and is used in natural repellents, candles and sprays. Congress grass is the weed Parthenium, elephant grass is a tall fodder and biomass grass, and nut grass is a sedge weed. Remember: lemongrass or citronella for mosquito repellent.
Why each option is right or wrong
- (a) Wrong: Congress grass is the invasive weed Parthenium, known for causing allergies.
- (b) Wrong: elephant grass is a fodder and biomass crop.
- (c) Right: lemongrass oil is used in natural mosquito repellents.
- (d) Wrong: nut grass is a sedge weed, not a repellent source.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2021, General Studies Paper I, Series A. The paper on upsc.gov.in.