When communicating with apollo astronauts, scientists on earth use radio waves and the "over to you" method of communication. this method must be used because of the delay in communication. this delay is due to the a) scattering of electromagnetic waves in space. eliminate b) fact that sound waves do not travel in a vacuum. c) poor reflective nature of the surface of the moon. d) distance to the moon and the speed of electromagnetic waves.

The answer is; D

While electromagnetic waves travel at an astounding 3.00 x 10^8 m/s and any delay seems imperceptible in short distances, in long distances, the waves take some time to reach the other end. This is why there is usually a small delay when ground communication tries to reach astronauts in space.  Also, remember that when a communication is relayed from the earth, it has to reach the destination and then wait for a response back to earth which covers the same distance or longer/shorter if the target is moving.

The distance to the moon is 384,400 km, therefore multiply this by 2 = 768,800 km

768,800,000m/300,000,000m = 2. 56 seconds

Therefore radio waves sent to the moon from earth will have a minimum  2.5  seconds delay not considering the processing time of this communication by the destination before sending feedback.  ‘Over to you’ signals end of a message by the messenger hence allowing the other messenger on the other to respond.