What is a vertex . Please explain Thanks..

Step-by-step explanation: In geometry, a vertex is where two rays share a common endpoint or where they interest each other.

The rays are called the sides of the angle and

common endpoint is called the vertex.

The vertex is very important when naming angles because

the vertex is always at the center when naming the angle.

Below is an example of two rays that share a

common endpoint which is called the vertex.

i believe it's a.

i'm not sure on this one, most likely correct.