usually you will see something like g(x) or f(x)
domain means all the x's
so, think of g(4) meaning g(x=4) and g(4 in the domain).
look for 4 on the domain side
you know that f(x) = y
range means all the y's
so its basically saying, look on the domain side for 4 and see what comes out (or =) on the range side.
in this case, it's B) 5