B

One night in February 1962, John H. Glenn, Jr. , flew over Australia. The man in the Mercury (水星号) capsule (太空舱) was alone, but friendly voices reached him by radio. On the dark land 100 miles below, he saw a sprinkling (零星) of lights. They marked the city of Perth, where people had turned on their lights as a greeting to him. In Friendship 7, Glenn radioed, "Tile lights show up very well. Thank everybody for turning them on." His capsule raced on to the east. During his three orbits of the earth, Glenn could always reach one of eigh tracking stations. Some of them were on ships at sea. Others were in the United States. Many of the stations had been built with the help of the other countries. These countries allowed Americans to bring in radio equipment and set it up. Without the help of such lands as Nigeria, Zanzibar, and Mexico, there would have been breaks in the worldwide radio network. John Glenn, Jr. , was the first American to orbit the earth. Pot his flight, the tracking network covered 60,000 route miles. Five hundred people worked in the stations along the route. Since his flight, the network has grown. Today, it covers more thanlO0,000 route mi- les and has about one hundred stations. One-third of these stations arc outside the United States.

It can be inferred from the story that ______