34. Cospas-Sarsat comprises a several near polar orbiting satellites and一． A: a network of land based earth stations B: several coast stations C: an earth station D: some RCCs

()service means a service which is based on polar orbiting satellites which receive and relay distressalerts from satellite EPIRBs and which provides their position . A: Geostationary satellite B: Near-polar orbiting satellite C: synchomizing satellite D. D: Terrestrial satellite

The low polar orbiting satellite system provides the coverage of （ ） A: Area A4 B: Area Aland A2 C: Area A3 D: Area Al. A2.A3and A4

25. The-low polar orbiting satellite system provides the coverage of _ A: sea areas Al and A2 B: sea areas AJ, A2, A3 and A4 C: sea area A3 . D: sea area A4

23. The low polar orbiting satellite system provides the coverage of____. A: sea area A4 B: sea areas Al and A2 C: all over the world D: sea areas Al, A2, A3 and A4

Unlike the American GPS, Russian GLONASS, and European Galileo systems, which use median Earth orbit satellites, BeiDou-1 uses satellites in （ ）. A: Geostationary orbit B: Circular orbit C: Sun-synchronous orbit D: Near polar orbit

Russian space __________ is currently orbiting the Earth.

No force of gravity acts on an astronaut in an orbiting space station.

By saying "Spring is usually prime food time for 1,200 polar bears" ( Line 1, Para. 1 ), the author means that ______. A: spring is usually a good time for polar bears to carry out their mating rituals B: the polar bears usually eat a lot in the spring C: spring is generally a good time to hunt polar bears D: polar bears usually hibernate in the spring

How is the future of polar bears?