Many experts agree that once these treasures are to the air great harm will be done to t

问题补充：

Many experts agree that once these treasures are to the air, great harm will be done to them. So they think it better not to unearth the treasures.

A. exposed

B. threatened

C. constructed

D. conserved

答案：

(答案→)A. exposed

B. threatened

C. constructed

D. conserved

解析： 词义辨析。Exposed暴露；threatened威胁；constructed建设；conserved

保护，保存。句意：许多专家同意一旦这些宝藏暴露于空气中，会对他们造成很大的伤害。所以他们认为最好不发掘这些宝藏。所以选A。