No light does not need medium to travel.Its an electromagnetic(EM) wave.All EM waves travel independent of medium. In contrast mechanical waves need a medium,sound waves,shock waves are mechanical and they need medium to transfer energy or travel.
The object is fixed relative to the motion you are trying to describe.
Electric force from electomagnetic force and force of gravity from gravitational force
Answer: D!
It is the option with the greatest amplitude.
