Which one of the following is used in preparing a natural mosquito repellent?
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Answer: C. Lemongrass oil, rich in citral, repels mosquitoes and is used in natural repellents. Its close relative citronella grass (same genus, Cymbopogon) gives citronella oil, another common repellent. Congress grass, elephant grass and nut grass are not used this way.
Watch for: Citronella is the giveaway; it comes from a grass of the lemongrass family (Cymbopogon).
Why the other options are wrong
- A. Wrong because Congress grass (Parthenium) is a harmful weed.
- B. Wrong because elephant grass is used as fodder.
- D. Wrong because nut grass is a weed, not a repellent source.
Source to check: CSIR-CIMAP (Central Institute of Medicinal and Aromatic Plants) website, Lemongrass
Answer from the official UPSC key. Written and fact-checked by AI against the official key. Spotted a mistake? Report it.