The correct answer is option 2. • Geostationary orbits (GEO) • Geostationary orbits of 36,000km from the Earth's equator are best known for the many satellites used for various forms of telecommunication, including television. • The speed of the satellite at this distance matches the earth's rotation, thereby keeping the satellite stationary over a particular point on the earth. Hence, statement (a) is true and is a reason of statement (b). • Telecommunication needs to "see" their satellite all time and hence it must remain stationary in the same positions relative to the Earth's surface. • The majority of communication satellites to date are in geostationary orbit, and this is expected to remain the case for some time. • Geostationary satellites support voice, data, and video services usually providing service to a particular region. Related Concepts: • Polar orbit • Satellites in polar orbits usually travel past Earth from north to south rather than from west to east, passing roughly over Earth's poles. • Satellites in a polar orbit do not have to pass the North and South Pole precisely; even a deviation within 20 to 30 degrees is still classed as a polar orbit. • Polar orbits are a type of low Earth orbit, as they are at low altitudes between 200 to 1000 km. • Sun-synchronous orbit (SSO) • Sun-synchronous orbit (SSO) is a particular kind of polar orbit. • Satellites in SSO, traveling over the polar regions, are synchronous with the Sun. • This means they are synchronized to always be in the same ‘fixed’ position relative to the Sun. • Transfer orbits and geostationary transfer orbit (GTO) • This allows a satellite to reach, for example, a high-altitude orbit like GEO without actually needing the launch vehicle to go all the way to this altitude, which would require more effort – this is like taking a shortcut. Reaching GEO in this way is an example of one of the most common transfer orbits, called the geostationary transfer orbit (GTO). • Lagrange points • Lagrange points, or L-points, allow for orbits that are much, much farther away (over a million kilometres) and do not orbit Earth directly. • These are specific points far out in space where the gravitational fields of Earth and the Sun combine in such a way that spacecraft that orbit them remain stable and can thus be ‘anchored’ relative to Earth.