Last week, I attended a lecture on lost     1    (文明). It was about Pompeii and Loulan, both of which were busy and w    2    about 2,000 years ago. F    3    in the 8th century, Pompeii was d    4    by a volcano, a natural     5    (灾难) that buried the whole city alive.    6    (与……不同) Pompeii, Loulan disappeared mainly because of the damage humans did to the environment. Once a     7    (商业的) city on the famous Silk Road between the East and the West, Loulan was covered with huge trees. But the trees were cut down and the city was     8     (逐渐地) covered over by sand. T    9     we ought to a    10    great importance to environment protection.