Why this Question: Sustainable agriculture has been the major aim of the Government. Also, water guzzling crops like sugarcane has been in news. 

Ans) a  

Exp) Option a is correct. 

Option a is correct. Sugarcane is the least water efficient crop. Among the given options, its water requirement is 1800-2200 mm/season which is highest.  

Option b is incorrect. Sunflower’s water requirement was estimated at 672.4 mm/season. 

Option c is incorrect. Pearl millet is a drought tolerant crop. 

Water requirement: 350 mm/season. 

Option d is incorrect. Red gram uses about 250-400 mm/season of water.  

Source:  http://www.ikisan.com/ka-redgram-water-management.html 

http://eagri.org/eagri50/AGRO103/lec07.pdf 

https://www.researchgate.net/publication/260793826_Water_Requirement_of_Sunflower_Helianthus_annuus_L_in_a_Tropical_Humid-Coastal_Savanna_Zone#:~:text=Water%20requirement%20of%20sunflower%20(by,season%20or%207.1%20mm%2Fday.&text=It%20was%20concluded%20that%20even,the%20productivity%20of%20the%20cro. 

 Subject) Geography