Exactly. It was the source and not light itself. Even if it had been the light, the answer would have been 300,000 and not 300,0100 as the speed of light remains constant according to einstein's theory of relativity.
eds portion was badly set, for example, in dams, the principle employed to generate electricity is to convert the gravitational potential energy of water into its kinetic energy. This option was there but I chose the option K.E to electricity which though is less commonly used when talking about hydro dams but seemed more close as it explained the end processes.
P.E----->K.E----->Mechanical energy------->Electrical energy
the question with reference to vacuum was also puzzling. it was something like that: the air inside a vacuum cleaner is............. with respect to atmosphere. Now two options, 'vacuum' and 'at low pressure', equally fit the answer, knowing that a perfect vacuum is impossible to achieve but the terminology is often used when pressure is significantly low and the other option 'at low pressure' is also not good enough since the pressure should not be just low but significantly low to generate suction effect but still it was technically correct . so my gut feeling triumphed over my knowledge and I went for the vacuum option keeping in view that it was EDS and not engineering paper, and the name is "Vacuum cleaner".
similarly, the thrust option of airplane engine though works against drag but at the same time, it helps in increasing the lift as well since the air speed around the wings increases with engine thrust and hence increased pressure difference results in lift.