Does sit down and hear make a sentence?

No, "sit down and hear" doesn't make a complete sentence. Here's why:

* Subject: A sentence needs a subject, the person or thing doing the action. We don't know who is doing the sitting and hearing.

* Verb: We have the verbs "sit" and "hear," but they need to be connected to a subject.

To make a sentence, you need to add a subject:

* Example: "You sit down and hear what I have to say."

Now we have a subject ("you") and the verbs "sit" and "hear" are connected to it.