Stuck on question

Question

If a and b are both odd integers, which of the following MUST also be an odd integer?

a+b

a-b

axb

a/b

Answer 1

if a and b are both odd

then

a+b is always even

a-b is always even

axb is always odd

a/b is an odd interger or a fraction

try two odd numbers 5 and 7

7+5 =12

7-5 = 2

7x5 = 35

7/5 = an improper fraction

but 9/3 = an odd number

3/9 = 1/3 a proper fraction

axb is the only correct answer