The colours we see are the wavelengths that are reflected or transmitted. For example, a red shirt looks red because the dye molecules in the fabric have absorbed the wavelengths of light from the violet/blue end of the spectrum.
The right answer is B, that kind of current is called also AC and you can look at the power supply module of your phone or computer - there will be an information about types of transformed currents, one of them is AC.
Explanation:
upthrust is the same as Force
And the dimension of Force is MLT-2
The -2 is going to be in raise to power form....
Hope it helps....
Assuming north as positive direction, the initial and final velocities of the ball are:

(with negative sign since it is due south)

the time taken is

, so the average acceleration of the ball is given by

And the positive sign tells us the direction of the acceleration is north.