题目选项分析

The survival of coral colonies, which are composed of innumerable tiny polyps living in a symbiotic relationship with brilliantly colored algae, are being threatened, experts say, by not only pollutants such as agricultural runoff, oil slicks, and trash, but also by dropped anchors, probing divers, and global warming.

The survival of coral colonies, which are composed of innumerable tiny polyps living in a symbiotic relationship with brilliantly colored algae, is being threatened, experts say, not only by pollutants such as agricultural runoff, oil slicks, and trash, but also by dropped anchors, probing divers, and global warming.