这是典型的宾语从句
这句缺少主语从句的引导词what.即：What I want to tell you is thatwe must take some effective measures at once. 这是一个含有主语从句与表语从句的复合句。
追答：因为 I want to tell you 这个句子作主语时没有引导词是讲不通的呀！再说了，及物动词tell 后面习惯带双宾语，即 tell sb sth./ tell sth. to sb.（告诉某人某事）。 what （在本句中的意思是：所...的事情）不但要引导主语从句，并且在句子中作直接宾语。
i want to tell you that什么句型
表语从句
That is what I want to tell you.那就是我想要对你讲的。这里what在表语从句中充当直接宾语。
希望我的回答对你有所帮助
i want to tell you that什么句型
"I want to tell you that" is a declarative sentence.
i want to tell you that什么句型
i want to tell you that是宾语从句。