secondary activity次级: secondary活性: activity; active; activated多级活性污泥处理: multistage activated sludge treatment班级活动: class work第二级活动: secondary activity; secondaryactivity下载手机词典可随时随地查词查翻译关注微信公众号：chachacidian，回复:次级活性，即可在微信中查询翻译
