Explanation:

All the above mentioned factors are correct.

Flash drought refers to a severe drought kind of situation that develops very rapidly. 

• Flash droughts are those that occur very quickly, with soil moisture depleting rapidly. 
• This happens because rains stay away for 15-20 days at a stretch.
• Normally, developing drought conditions take months, but these happen within a week or in two weeks’ time in abnormal conditions. 
• In India, 82 per cent of such extreme weather events happen during the monsoon period.
• Factors behind: Several factors including atmospheric anomalies, anthropogenic greenhouse gas emissions, summer monsoon precipitation, sea surface temperature, role of El Nino Southern Oscillation, and air temperature over India play an important role.

Hence option 4th is correct.