Question:
If n is even, which of the following cannot be odd?
I n + 3
II 3n
III n² - 1

Option A):
I and II only
Option B):
III only
Option C):
II only
Option D):
I, II and III

Correct Answer is Option C):
II only

Explanation:
In case I , even plus odd will give odd
In case II, odd times even will give even
In case III even squared is even, and even minus odd is odd.
(You can check this by using an easy even number like 2 in place of n)
Only case II cannot be odd.