S1: Drought is a continuous and lengthy period during which no significant rainfall is recorded during the rainy season.
S6: In India, droughts are more frequent in the areas where the average annual rainfall is less than 60 cm and the variability of rainfall is over 20 per cent.
P: This definition however, does not apply to Mawsynram and Cherrapunji, where even one week recording less than 0·25 mm of rainfall may be considered as a drought period.
Q: In general, the areas recording less than 60 cm of rainfall annually and in which the variability of rainfall is more than 20 per cent are the drought prone areas in India.
R: In India, the Meteorological Department has defined drought as a period of at least 22 consecutive days on none of which is there more than 0·25 mm of rainfall.
S: Areas where the variability of rainfall varies between 20 to 60 per cent are the chronic drought prone areas.

The correct answer is 'Option 4'.

Key Points

• S1: Drought is a continuous and lengthy period during which no significant rainfall is recorded during the rainy season.
  • This sentence provides a general definition of drought.
• R: In India, the Meteorological Department has defined drought as a period of at least 22 consecutive days on none of which is there more than 0·25 mm of rainfall.
  • This sentence logically follows S1 by giving a specific, official definition of drought as applied in India.
• P: This definition however, does not apply to Mawsynram and Cherrapunji, where even one week recording less than 0·25 mm of rainfall may be considered as a drought period.
  • The phrase "This definition however" in P directly refers to the definition given in R and presents an exception to it, creating a strong cohesive link.
• Q: In general, the areas recording less than 60 cm of rainfall annually and in which the variability of rainfall is more than 20 per cent are the drought prone areas in India.
  • After defining drought and its exception, the paragraph shifts to defining "drought prone areas." Q provides a general criterion for these areas in India, based on rainfall and variability.
• S: Areas where the variability of rainfall varies between 20 to 60 per cent are the chronic drought prone areas.
  • This sentence further refines the definition of "drought prone areas" from Q, specifically classifying "chronic" ones based on a more precise range of rainfall variability.
• S6: In India, droughts are more frequent in the areas where the average annual rainfall is less than 60 cm and the variability of rainfall is over 20 per cent.
  • This concluding sentence reinforces the criteria for drought-prone areas/frequency discussed in Q and S, acting as a summary.
• The sequence R-P-Q-S creates a coherent flow from the general definition of drought (S1), to India's specific definition (R) and its exception (P), then to the general characteristics of drought-prone areas (Q), and finally to a more specific category of chronic drought-prone areas (S), leading to the concluding statement (S6).
   

Coherent paragraph after rearrangement:

S1: Drought is a continuous and lengthy period during which no significant rainfall is recorded during the rainy season.
R: In India, the Meteorological Department has defined drought as a period of at least 22 consecutive days on none of which is there more than 0·25 mm of rainfall.
P: This definition however, does not apply to Mawsynram and Cherrapunji, where even one week recording less than 0·25 mm of rainfall may be considered as a drought period.
Q: In general, the areas recording less than 60 cm of rainfall annually and in which the variability of rainfall is more than 20 per cent are the drought prone areas in India.
S: Areas where the variability of rainfall varies between 20 to 60 per cent are the chronic drought prone areas.
S6: In India, droughts are more frequent in the areas where the average annual rainfall is less than 60 cm and the variability of rainfall is over 20 per cent.