Now, the thing you have to remember about " set" , this is called an ambitransitive verb.
现在，你必须记住关于“set”的事情，这叫做双及物动词。
Engvid-Adam-课程合辑
Some are called ambitransitive, means in some situations, they take an object; in some situations, they don't take an object.
有些被称为双向传递， 意思是在某些情况下， 他们接受一个对象；在某些情况下， 他们不拿东西。
Engvid-Adam-课程合辑
You don't need to know that word " ambitransitive" , but it means it can be a transitive or an intransitive, meaning it can take an object or not take an object.
An ambitransitive verb is a verb that can be intransitive or transitive without requiring a morphological change. That is, the same verb form may or may not require a direct object. English has a large number of ambitransitive verbs. Examples include read, break, and understand (e.g., "I read the book," saying what was read, or just "I read all afternoon").