单选题 Recent studies have identified four major global environmental risks; acid rain, ozone depletion, deforestation and the greenhouse effect.
A. recognized B. proved C. got rid of D. multiplied

【正确答案】 A
【答案解析】recognize认可，承认；prove证明，检验；get rid of消除；multiply繁殖，增加；identify识别，鉴别。