I do not know the reason why he looks unhappy today.the reason后的why可不可以换成that,如果可以,他们有什么区别?如果不可以又为什么?要怎么区别the reason后面什么时候用why什么时候用that 麻烦清楚一点

I do not know I do not know Do not know what you're talking? You're online every day,will not help the open window,or you want to know you.Always I am still waiting,but you do not have to I Know You're Not Alone 歌词 I do not know the w__ to the library am so hypocritical you, you gave me the chance I did not cherish, I know're wrong, I'm sorry, I do not ask you for the opportunity, but I will contin 的完全中文意思 I did not like the man.Do you know? If I do not know how good that the翻译 I do not know the k( )to these questions. I do not know the car ____the color is blue. I do not know where is the problem I do not know a______ to the q______ . i do not know where--------- (buy)the dress 请问 I DO NOT KNOW sorry,i do not know! Why I do not know -I do not know what the new word means. - I do not,_____