On the 40th Earth Day Dr Wang gave us a talk on the importance of the earth.A. practicin

问题补充：

On the 40th Earth Day, Dr Wang gave us a talk on the importance of the earth.

A. practicing

B. preventing

C. polluting

D. protecting

答案：

A. practicing

B. preventing

C. polluting

(答案→)D. protecting

解析：本题考查词义辨析，practice：实践；练习；prevent：预防；阻碍；阻止；pollute：污染；玷污；破坏；protect：保护，保卫。根据句意，应为“在第四十个地球日，王博士给我们作了关于保护地球的重要性的报告。”应为保护地球，选D。