The function f is given by f(x)=x³+x.
Which of the following statements is true and supports the claim that f is an odd function and not an even function?
1) The graph of f is symmetric about the y-axis.
2) The graph of f is symmetric about the origin.
3) The graph of f is increasing for all values of x.
4) The graph of f is decreasing for all values of x.