Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

If x and y are integers, is xy an even?

1) x is an odd

2) y is an even

In the original condition, there are 2 variables(x,y), which should match with the number of equations. So you need 2 equation. For 1) 1 equation, for 2) 1 equation, which is likely to make C the answer. When 1)&2), they become xy=odd*even=even, which is yes and C is the answer. This question is also an integer question, which is a key question. Apply the mistake type 4.

For 2), if y=even, xy=even is always valid, which is yes and sufficient.

For 1), suppose x=odd=1. If y=2, it is yes but if y=1, it is no, which is not sufficient.

Therefore, the answer is B.

This is the mistake type 4(A).

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