A. It was doomed for the start.
B. It turned out to be a disaster.
C. It was spolied by one girl.
D. All the students enjoyed it.
A. A thrilling exploration in the desert.
B. How GPS saved the survivors.
C. What is GPS and how it works.
D. The danger of space exploration.
A. It was created mainly for scientific research.
B. It works better in fine weather conditions.
C. It must be located on at least three satellites.
D. Its service is free of charge.
A. The user's position.
B. The speed of the satellites.
C. The distance to destination.
D. The information to the earth.