Operation Green Hunt is the correct answer.
When the Union government and various state governments joined forces to push back against Naxalite or Maoist insurgents operating across the tribal and forested belt known as the Red Corridor, the resulting security campaign became widely known as Operation Green Hunt. It brought together central paramilitary units like the CRPF with state police forces in states such as Chhattisgarh, Jharkhand, Odisha, and West Bengal, with intensified action seen through 2009 and 2010.
The term Operation Green Hunt spread through news coverage and public commentary as the label for this campaign, referencing the green, forested terrain where much of the conflict played out. None of the remaining choices, Operation Red Alert, Operation Cobra Den, or Operation Clean Corridor, match the actual name that was used for this anti-Naxalite drive, they are simply invented distractors.
So, the campaign waged by Union and State Governments against Naxalites is known as Operation Green Hunt, confirming option 2.