Answer
$a$ is the acceleration
$b$ is the velocity
$c$ is the position function
Work Step by Step
As $b$ has a horizontal tangent and changes from rising to dropping. $a$ crosses the $t$ -axis between the positive and the negative, thus
$a$ is the derivative of $b$
The tangents of $c$ have positive slope for the whole graph, and are close to horizontal at the left and the right ends. The graph of $b$ is positive throughout and is close to 0 at the ends, thus
$b$ is the derivative of $c$
