Answer
The correct option is (c)
$10\ \rm km/h^2$ due east
Work Step by Step
We know that acceleration is the rate of change of velocity, i.e.
$a=\dfrac{v-u}{t}$
Where $v$ is the final velocity, $u$ is the initial velocity, and $t$ is the time.
$a=\dfrac{65\ \rm km/h-80\ \rm km/h}{1.5\ \rm h}$
$a=-10\ \rm km/h^2$
The negative sign implies that the train is slowing down, hence we can say that the acceleration of the train is $10\ \rm km/h^2$ due east.
