Which of the following pairs has same dimensions?

The relation between time $t$ and distance $x$ of a particle is $t=a x^2+b x$, where $a$ and $b$ are constants. If $v$ is the velocity of the particle, then its acceleration is

A bomb is dropped on an enemy post on the ground by an aeroplane flying horizontally with a velocity of $60 \mathrm{kmh}^{-1}$ at a height of 490 m . At the time of dropping the bomb, the horizontal distance of the aeroplane from the enemy post, so that the bomb hits the target is

The angular speed of a particle moving in a circular path is doubled. Then, the centripetal acceleration of the particle is