Explanation:

 2 only 

• Cloud seeding is a kind of weather modification technology to create artificial rainfall.
• It works only when there are enough pre-existing clouds in the atmosphere.
• Rain happens when moisture in the air reaches levels at which it can no longer be held, and cloud seeding aims to facilitate and accelerate that process by making available chemical ‘nuclei’ around which condensation can take place.
• These ‘seeds’ of rain can be the iodides of silver or potassium, dry ice (solid carbon dioxide), or liquid propane. The seeds can be delivered by plane or simply by spraying from the ground.

Where all has it been tried earlier?

• Cloud seeding is not new to India and it has earlier been attempted in Karnataka, Andhra Pradesh and Maharashtra to address drought.
• Similar experiments of cloud seeding had earlier been tried in Australia, America, Spain and France.
• In United Arab Emirates, the cloud seeding technique led to creation of 52 storms in Abu Dhabi.
• Till last year, IMD had around 30 successful incidents of seeding.
• Also, such seeding is routine in Russia and other cold countries where the technique is used to disperse fog at the airports.