If a and b are integers and a²b is odd, all of the following must be odd EXCEРТ-

Question: If a and b are integers and a²b is odd, all of the following must be odd EXCEPT -

Solution:
a²b is odd ⇒ a² is odd and b is odd ⇒ a is odd and b is odd.
For odd a and odd b:
a is odd, b is odd, ab is odd,
ab - a is even because two odd numbers subtraction is always even.