Question

Sandra, you just met your new boss. What expression could you use at the end of the conversation?

¿Qué tal?
¿Cómo estás?
Hola.
Encantada.

Answer 1

The first 3 options are examples of phrases which would be used as greetings ( ¿Qué tal?== What's up?; ¿Cómo estás?==How are you?; Hola==Hello), so they would not be used at the "end of the conversation".
The fourth option, "Encantada", literally means "delighted" and can be used to say "It's nice to meet you" or "It's been nice talking to you"

As the other users mentioned, this would probably be the best answer, but it is generally not best practice on this site to give direct answers without explanation. Just something to keep in mind moving forward :)