Statement 1 => s is divisible by 3
This means s must be a multiple of 3
There are 2 possibilities for r, it is either r is a multiple of 3 as well or r is not a multiple of 3
Based on the fact that r+s must be divisible by 3 i.e r+s is a multiple of 3
If s = 6 and b = 9 then 6 + 9 = 15 (multiple of 3) but if s = 9 and b = 5 then 9+5 = 14( not a multiple of 3)
Since there is no specific information on r, the target question cannot be evaluated and statement 1 is NOT SUFFICIENT


Statement 2 => r is not divisible by 3
This means r is not a multiple of 3. There are 2 more possibilities for s, either it is a multiple of 3 or it's not a multiple of 3
If s = 6 and r = 5 then 6+5 = 11 (not a multiple of 3)
If s = 7 and r = 2 then 7+2 = 9 (multiple of 3)
Since there is no specific information on s, the target question cannot be answered and statement 2 is NOT SUFFICIENT


Combining both statements together =>
From statement 1 => s is a multiple of 3
From statement 2 => r is not a multiple of 3
If s = 6 and r = 5 then 6+5 = 11 (not a multiple of 3)
If s = 9 and r = 4 then 9+4 = 13 (not a multiple of 3)
With the information provided, we have ascertainment that multiple of 3 + non-multiple of 3 = non multiple of 3, hence it is not divisible by 3.


Combining both statements together was SUFFICIENT,
Answer = C