difficult of难以, 很难
difficultadj.困难的;艰难的;(人)难对付的;不易相处的
difficult function unit困难功能元
difficult circumstances艰苦的环境
difficulties on culture通识教育
difficult communication可听度差
difficulties in finance融资困难
difficulties in studying学习困难
difficult flotation ores难选矿石
difficulties of teaching教学困惑
difficult and easy level难易程度
difficult mining orebody难采矿体