It is economical to run and ecologically sound.跑步不仅省钱而且环保。Can anyone suggest a method of deterring spiders which is ecologically sound?有人能想出一种不会破坏生态环境而又能够赶跑蜘蛛的办法吗？Poisoning the earth's atmosphere is ecologically and morally unjustifiable.污染地球的大气在生态上和道德上都是不能接受的。