...fast, didn't, how to, ahead of,how, difficult,英语替换答:that , as we all know that...nervous: tight, tense, anxious, embarrassed...very fast: rapid, fleet, quick, swift, soon, before long, hurry up...didn't: (这个没必要替换吧?)never ahead of: before how(这个也无需替换啊?)difficult: hard, not easy, almost impossible......