Read the followingpassage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions.

Mars has captured the imaginations of people since ancient times. People have long wondered if the planet is home to alien life. Over the years, a number of theories con-cerning this matter have arisen. In the nineteenth century, there were finally telescopes made that could closely examine at the surface of the Red Planet. While looking at Mars, an Italian astron-omer saw many straight channels on its surface. These were most likely caused by the action of either the wind or water in the distant past. When he published his observations, he used the Italian word canali, which means "channels". However, English-speaking astronomers interpreted the word as "canals" and assumed that he was referring to something akin to manmade canals on Earth. An American astronomer. Percival Lowell, believed that these "canals" had been built by a race of intelligent beings that had lived - and might still be living - on Mars. The result of that highly publicized claim was that a great number of myths about Mars suddenly arose. For instance, H. G. Wells wrote The War of the Worlds, a book about a Martian invasion of Earth, in 1898. Over the next few decades, Mars and Martians featured in countless science fiction stories, movies, and TV shows. Years later, in the 1960s and 1970s, the United States sent several satellites to investigate Mars more closely. The satellites found no canals. but one picture sud-denly ignited a great deal of interest in Mars. In 1976, Viking 1 took a snapshot of the Martian surface. In the picture was what appeared to be an enormous human face. It was so large that it measured more than three kilometers long. This con-vinced people that there was - or had been - intelligent life on Mars. In 2001, however, the mystery of the Martian face was solved by Mars Global Surveyor. The pictures that it transmitted proved that the face was just a mesa, a type of geological formation. As for the "eyes, nose, and mouth" of the face, they were merely shadows. Despite this proof, many people are still convinced that signs of life could be found on Mars someday.

What did Mars Global Surveyor do?