Why this question: 

•  In late 2019, the Uttarakhand government had decided to carry out bio-fencing to reduce man-animal conflict by growing various species of plants (including lemongrass).  

• A new variety of lemongrass was reported (in January 2020) to be grown by tribals of Anamalai forests. 

Ans) c 

Exp) Option c is correct. 

Option c is correct. Lemongrass is a tall herb that is abundantly found in tropical and sub-tropical areas of Asia, Africa, and Australia. China and India accounts for the maximum production of Lemongrass. 

The Lemongrass plant is known to be an excellent mosquito repellent. It contains a compound citronella that helps to mask the scents that mosquitoes rely on to target hosts. According to a study conducted in 2011, around 95% mosquitos from a specific range of species were either killed or completely repelled due to the intense odour of lemongrass oil. 

Source:  Is Lemongrass Mosquito Repellent? – Conserve Energy Future (conserve-energy-future.com) 

Subject) Environment