Correct Answer - Option 4 : 14
The logic followed here is:
1) Number of letters in RESERVOIR is 9.
So, RESERVOIR is written as 9.
2) Number of letters in PRESERVING is 10.
So, PRESERVING is written as 10.
Similarly;
3) Number of letters in CONGRATULATION is 14.
So, CONGRATULATION is written as 14.
Hence, "14" is the correct answer.