The 24 satellites in the Global Positioning System ( GPS ) are synchronous satellites, and they appear to be stationary to an observer on the earth.

These satellites constantly transmit an identifying .

One or two man-made satellites _______ in this country every year.

Geostationary satellites are the man-made satellites which . A: are always fixed in the regular position B: sometimes move with the earth C: are synchronizing with the movement of the earth D: can not fly off from the ground

Why do we use the weather satellites to take pictures of the atmosphere? Because __________.

The photos of Mars taken by satellites are (clear) ______ man those taken from Earth.

It is possible to use satellites to predict earthquakes because satellites ________. A: take pictures of the Earth B: catch radio waves sent from the Earth’s surface C: are sensitive to Earth’s movements D: see almost the entire Earth

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

GPS satellites send signal information, such as time, position of satellite, position of receiver, and traffic condition on the earth.

At least ( ) satellites are required to calculate the distance from the satellite to the receiver. A: Six B: Four C: Three D: Five