书上有个选择题（ ）I am,it is useful to know foreign languages答案是what

书上有个选择题（ ）I am,it is useful to know foreign languages答案是what I thought ______very useful to know the customs of foreign c To learn a foreign language well is useful ,I think.I think_ I think that it's a useful to learn a foreign-language. ( )I know what it is to be in need and what it is to have __ we all know it 's useful ______English well.为什么是to learn ,有什 英译汉Foreign Languages Department,a cheking machine is used to foreign languages ___very difficult to learn 填is还是are What ------ useful advice it is! to learn a foreign language well is useful,I think(改为同义句) 几个英语小问题1.To learn a foreign language well is useful,I think. I find that it is useful to learn English.it是形式主语,