The correct option is C Period is equal to the period of rotation of the earth about its axis
Satellites in orbit cannot pass along their information to the ground stations on Earth if the satellite does not have a clear view of the ground station.
Relay satellites are the type of geostationary satallites.
So, relay satellites being geostationary satellites rotate along with the ground stations and thus always have a clear view.
Hence, the period of satellite is equal to period of rotation of earth and it seems to be at one point about the equator and so is able to transmit the signals from one part to other.
Hence, option (d) is correct answer.