An American professor who studied the Mayas has come up with a new theory about the sudden end of their empire. (0) ______ to Professor Richard Hansen, an archaeologist at the University of California, the (1) ______ of the Mayan civilization in Central America was (2) ______ about by the Mayas themselves.
Their object was to display their wealth and power by making their buildings and decoration as beautiful as possible. This (3) ______ using large quantities of lime, which they put on the walls to make them smooth. Unfortunately, the creation of lime is a process which requires intense heat, and they therefore (4) ______ to cut down huge numbers of trees. This affected the quality of the soil, and it became almost impossible to farm.
Professor Hansen, who has (5) ______ returned from an excavation in the El Mirador region of northern Guatemala, told a meeting of archaeologists in Philadelphia that the Mayas, having (6) ______ this mistake in the 3rd century, repeated it 600 years later, at which time it proved fatal. Increasing food (7) ______ among the Mayas created a Central American equivalent of the Peloponnesian War which ravaged ancient Greece. However, (8) ______ the Greek civil war, which only (9) ______ for 27 years, the Mayas wars went on for many centuries and left many of their great cities and temples in (10) ______ .

0.
A. Referring
B. Relating
C. According
D. Respecting
1.
A. collapse
B. drop
C. crash
D. stop
2.
A. made
B. came
C. turned
D. brought
3.
A. depended
B. needed
C. involved
D. requested
4.
A. obliged
B. forced
C. must
D. had
5.
A. still
B. just
C. already
D. yet
6.
A. done
B. had
C. taken
D. made
7.
A. lack
B. shortages
C. droughts
D. failures
8.
A. unlike
B. apart
C. without
D. unless
9.
A. stayed
B. spent
C. lasted
D. longed
10.
A. injuries
B. damages
C. spoils
D. ruins