Given that,
(I) K: { ...,-x^2, x, -x, x^3,... }
(II) K: { ...,-x^2, -x ,x, y, xy, x^2y,...}
1)Now, 2 is in K
If only 2 is in K, K: { ...,-4, -2, 2, 8,...} => 12 is not in K
Considering other numbers, say 6 is also in K, K: { ...,-12, -6, -2, 2,6, 12...} => 12 is in K
K may or may not contain 12.
Hence, NOT SUFFICIENT
2)3 is in K
If only 3 is in K, K: {...-9,-3,3,9,...} => 12 is not in K
Considering other numbers say, 4 is also in K, K: {...,-12, -4,-3,3,4,12,...} => 12 is in K
K may or may not contain 12.
Hence, NOT SUFFICIENT
Combining (1) and (2),
2 is in K and 3 is in K,
K: {...,-12, -9, -3, -4, -2, 2, 3,4, 8, 12...} => Irrespective of any other numbers, K definitely contains 12.
Hence, C.
