Answer: The correct answer is D, Lines are skew if and only if they are non-coplanar.
In geometry, lines are said to be skew if they are non-coplanar, meaning they do not lie in the same plane. They also do not intersect.
Option A is incorrect because angles can be supplementary (add up to 180 degrees) even if they do not form a linear pair (meaning they do not share a common vertex and a common side).
Option B is incorrect because Valentine's Day does not always fall in February. It is February 14th, but it could fall on a different month in a different year.
Option C is correct because a number is even if and only if it is divisible by 2. An even number can be divided evenly by 2, while an odd number cannot.
