Explanation:

first term = 121 
2nd term = first term-2^2 = 121-4=117 
3rd term = 2 nd term- 3^2=117-9=108 
4th term= 3rd term - 4^2 =108-16=92 
5th term= 4th term- 5^2 =92-25=67 
6th term= 5th term - 6^2= 67-36= 31 and so on 
so ans is (A) = 31

Hence, option 2 is the correct answer.