Why are geostationary satellites not useful for the study of the earth's polar regions?

1. Geostationary satellites orbit above the equator at a fixed point. 2. From an equatorial position they cannot view the polar regions well, so they are not useful for polar studies. 3. For polar coverage, elliptical medium-earth polar orbits passing over the poles are used instead. 4. The 90-minute period (rule out) belongs to Low Earth Orbit satellites, not geostationary ones. So the reason is their equatorial orbit. _Source: Balbharati (Maharashtra Board) Class 10 Science & Technology, Ch 10 "Space Missions", p.148_