Question

not to 和 don't 的区别。

We are often warned,by our teacher,______waster precious time because time will never return. 为什么这里要用not to 而不用don't 求详细解释 谢谢。

Answer 1

谓语动词是实意动词时，用don't 对谓语进行否定；
而该句中并非是对谓语的否定，而是对不定式的否定。
分析：by our teacher 是插入语，没插入时是：we are often warned to waste precious time,
对不定式to waste 进行否定，直接在不定式前加not，就成了：
we are often warned not to waste precious time.
加入插入语就成了原句的情况：we are often warned， by our teacher, not to waste precious time.

Answer 2

前面是动词的时候用not to ，本句前面是warn后面就要跟not to
don't前面要么是主语，要么是祈使句，直接以don‘t开头