很高兴为你解答!
主要是意思的不同,unless=if ……not,“除非,如果不”；as long as=so long as,“只要”；provided that=supposing that=given that=if,“如果,假设,假如”.
You can watch this film as long as / provided that you are not under 18.
只要/如果你不是18岁以下,你就可以看这部电影.
这题不可变成: you can watch this film unless you are not under 18.
可以变成you can‘t watch this film unless you are under 18.
另外,unless 你打错了.
希望对你有所帮助.学习进步、快乐!
�һ��Dz�����, you can watch this film unless you are not under 18.����㲻��18��, ��Ϳ��Կ��ⲿ��Ӱ, ����Ϊʲ�N������?лл!unless本身就是否定的意义的词，引导的句子用肯定形式，一般用not……unless……翻译为“除非……才……”。