Answer
$a=f'''(x)$
$b=f''(x)$
$c=f'(x)$
$d=f(x)$
Work Step by Step
First we analyze the "d" graph, because it's the graph with more intercepts, we notice that it has 2 intercepts at the origin, and there's only one graph that fulfills this condition, the "c" graph, so:
$d=f(x)$
$c=f'(x)$
Then we analyze the "c" graph, we notice that it has 1 intercept at the origin and that at the left it descends and to the right it ascends, the graph that fulfills those conditions is the "b" graph.
$b=f''(x)$
For last we analyze the "b" graph, it has 1 incercept at the origin and ascends in both, left and right, clearly the "a" graph,
$a=f'''(x)$
