Citizens of many countries are expressing concern about the environmental damage caused by the widespread release of greenhouse gases, damage that may be impossible to reverse. 在这个地方“,”后面加demage是什么用法。不是说","不能直接连接两个独立的句子吗?怎么没有连接词呀?(这句话是曼哈顿语法书中的正确的一句)不是很懂....请教各位,谢谢!!!