标题: 阅读里的语法问题，求解 [打印本页] 作者: lpbird 时间: 2011-9-14 11:56 标题: 阅读里的语法问题，求解 Low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be repopulated should the fish there disappear.an environmentally degraded stream could be recolonized by new salmon populations should the stream recover