Lidar，short for "light detection and ranging"，involves directing a rapid series of laser pulses- between 100，000 and 400，000 per second—at the ground from an airplane or a drone.Software captures the time and wavelength of the pulses reflected from the surface and combines it with GPS and other data to produce a precise three-dimensional（三維的）map of the landscape below.These high-tech explorations have revealed long-buried Mayan cities，including Tikal，in the dense jungle of Guatemala，and Caracol，in Belize.
   In recent years，lidar exposed an ancient city in western Mexico called Angamuco.The discovery of this long-lost Mexican city is especially significant.Built by the Purepecha，who were enemies of the Aztecs，Angamuco was a major civilization in the early 16th century，before Europeans arrived.
   "To think that this massive city existed in the heartland of Mexico for all this time and nobody knew it was there is kind of amazing，" says Chris Fisher，an archaeologist（考古學(xué)家）at Colorado State University who led the exploration.
   The city extended over ten square miles before it was covered by a lava（巖漿）flow. "That is a huge area with a lot of people，" says Fisher. "You are talking about 40，000 building foundations，which is [about] the same number of building foundations that are on the island of Manhattan."
   Archaeologists were surprised when they saw Angamuco's city plan.The Purepecha's monuments were largely concentrated in eight zones around the edges rather than being located in one large center.Why this almost Los Angeles-type sprawl（隨意）？Historians want to know the answer to that too.
   The revelation of Angamuco is an example of the power and promise of lidar.Archaeologists discovered signs of the buried city in 2007 and initially attempted to explore it using a traditional "boots on the ground" approach.But the team soon realized that with the rugged terrain（畸嶇的地形），it would take at least a decade to outline the entire metropolis.
   In 2011，they began using lidar to map nearly 14 square miles，revealing some astonishing features，from pyramids and temples to road systems，garden areas，and even ball courts.This gave them the "map" they needed to know where to explore further.So far，F(xiàn)isher and his team have verified more than 7，000 architectural features over a 1.5-square-mile area，with digging undertaken at seven locations.
   All told，researchers now believe that more than 100，000 people lived in Angamuco from about AD 1000 to AD 1350.That makes it the biggest city in western Mexico at the time―or at least the biggest city we know about so far
   "Everywhere you point the lidar instrument，you find new stuff，" says Fisher. "Right now，every textbook has to be rewritten，and two years from now，they're going to have to be rewritten again."

（1）Which of the following statements is true of Angamuco？

D

D

A．It was constructed by Aztecs.
B．It is a major civilization of Mexico.
C．It was destroyed in the early 16th century.
D．It came into existence before Europeans arrived.
（2）What has helped archaeologists find that Angamuco is a large area with a large population？

C

C

A．Its long history.
B．Its being unknown for long.
C．The number of building foundations in it.
D．The competition between Aztecs and it.
（3）Which of the following is still a mystery to historians？

A

A

A．The reason for Angamuco's city plan.
B．The reason why Angamuco disappeared.
C．The role Angamuco played in history.
D．The role Angamuco played in archeology.
（4）What does the revelation of Angamuco illustrate？

B

B

A．Mexican history is worth exploring.
B．Lidar is a useful tool for archeologists.
C．Maps are important in exploring historical sites.
D．More time needs to be devoted to studying Angamuco.