k Road, Loulan is believed to have been gradually covered over by sandstorms from AD 200 to AD 400.

楼兰是著名的丝绸之路的一个中转站，据说在公元200年至公元400年期间，它逐渐被沙尘暴覆盖。

?base

n.基础;底部;垒

adj.卑鄙的;低劣的

vt.以…作基础

?例句:

A business can only be built and ex

anded on a sound financial base.

一家企业只有在稳定的财政基础上才能开办并扩大规模。

?at

resent

na.目前

?例句:

At

resent, throughout the world, over 80% of the land that is suitable for raising cro

s is in use.

目前，在世界范围内，80%以上适合种植农作物的土地都在使用中。

?gradual

n.弥撒升阶圣歌集

adj.逐渐的;平缓的

?例句:

The greatest ho

e for reform is the gradual s

read of information.

改革的最大希望就是信息的逐渐传播。