which biconditional is not a good definition?

Question

1. a whole number is odd if and only the number is not divisible by 2
2. an angle is straight if and only if its measure is 180
3. a whole number is even if and only if it is divisible by 2
4. a ray is a bisector of an angle if and only if it splits the angle into two angles

Answer 1

r.i.p. Ms. Sue, may you fly high

Answer 2

The fact that no one responded.... still.

Answer 3

2. an angle is straight if and only if its measure is 180
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