The answer is 2) Num%2==1.
The modulus operator (%) divides the left hand side by the right hand side and returns the remainder.
Examples:
3%2=1 : 2 goes into 3 once, with 1 remaining.
5%2 =1 : 2 goes into 5 twice, with 1 remaining.
11%2 =1 : 2 goes into 11 five times, with 1 remaining.
