Answer
(F)
Work Step by Step
Before $x = 0$, or when $x < 0$, the line has a slope of $-1$ and an intercept of $0$, so the graph is $y = x$.
After (and including) $x = 0$, or $x\geq 0$, the line has a slope of 3 and an intercept of 0, so the graph is $y = 3x$.
This leaves us with (F).
