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Using (1)
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n^2 + n = n (n+1)
n^2 + n is not divisible by 3
==> neither n is divisible by 3 nor n+1 is divisible by 3
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12
If n and n+1 are not divisible by 3 means n-1 HAS TO BE divisible by 3
Easy way to explain is, by looking at example from above numbers
if n=4 n+1=5 n-1=3, divisible by 3
if n=1 n+1=2 n-1=0, divisible by 3
Sufficient
Using (2)
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3n+5 >= k+8, where k is a positive multiple of 3
Assume k = 3t
3n+5 >= 3t+8
n > = t+1
n-1>=t
==> t can further be multiple of 3 or it cannot be
Not sufficient.
Answer (A)
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