I don’t know _______ they have passed the exam.这里答案是if/whether,但是我觉得when跟how填进去也说得通啊.请问为什么不能填when跟how、?

I don't know his _______(话) 同义句转换:i don't know i've_____ _______.:i don't know i've_____ _______. i don't know what to say 同义句i _______ _______ _______ what to say I don't know how I can swim well.（改为简单句） I don't know ________ _______ _______well.I don't know how I can swim well.（改为简单句）I don't know ________ _______ _______well. I don't know. I don't know what shuold I do 的同义句是什么?I don't know _____ _______ _________ I don't know what I'm going to say at the meeting(改同义句)I don't know _______ _______ _______ at the meeting “i don't know you know i don't know I don't know where he _______ (hide) in the park.I can't find him 我不知道他为什么喜欢海豚：I don't know _______ _________ _________ _______. I don't know where I should go this afternoon.(改为同意句)I don't know _______ _______ _______this afternoon.爪机党手打不容易 I don’t know where the key is,but I suppose I _______ it at home. I know ______ is _______ brother,but I really don't like填单词 I don't know what I want _______(do).用正确形式填空 I don't know how _______(fly) the kite .I ask him______help(介) sorry,I don't know. i don`t know much I don't really know.