Since f(x) and g(x) are odd function, then
Their sum must be an odd function
Their product must be an even function
f(g(x)) means g(x) is the x of f(x)
Let us check it
f(x) is odd and g(x) is odd, then f(g)(x) is also odd
I is odd
II is odd
III is even
Then the answer is I and II only
