A. From its origin. B. From its length. C. From its colour. D. From its genes.
A. 生物因素 B. 化学因素 C. 物理因素
A. 臭氧层破坏 B. 酸雨 C. 温室效应
A. 急性危害 B. 慢性危害 C. 远期危害 D. 非特异性损害
A. 200 B. 250 C. 300 D. 275