I am installing a emergency exit sign that needs to be hard

JustAnswer Customer: I am installing a emergency exit sign that needs to be hard wired.
JustAnswer Customer: What size romex wire should I use and does it need to be on it own breaker switch?
Alex: Master Electrician: My name is XXXXX XXXXX I'm here to help you.
Alex: Master Electrician: I usually try to put exit sign on the lighting circuit , that way if breaker trips and lights go out the exit/ emergency lights will come on.
Alex: Master Electrician: Use 12/2 wire to be safe.
Alex: Master Electrician: If its commercial building you should use MC and not romex.
Alex: Master Electrician: Check what type of wiring is done .
Alex: Master Electrician: Let me know .
JustAnswer Customer: It is a commercial building.
JustAnswer Customer: Not familiar with the term MC.
JustAnswer Customer: What does it stand for?
JustAnswer Customer: Also there are 5 other emergency exit signs that exist.
JustAnswer Customer: I am adding one into it.
JustAnswer Customer: Should I run the new exit sign wiring directly to the lighting circuit at the panel?
Alex: Master Electrician: It's best to run wire from existing exit signs.
Alex: Master Electrician: What type of wires are ran now?
JustAnswer Customer: Are you saying to run all the exit signs in a loop and not individually back to the circuit breaker?
Alex: Master Electrician: Each exit sign does not have to be dedicated circuit from panel.
Alex: Master Electrician: They are jumped ( looped ) between each other.
Alex: Master Electrician: So if you already have existing exit sign then just tap to the nearest one.
Alex: Master Electrician: Let me know if you have more questions.
JustAnswer Customer: Great!
JustAnswer Customer: What does the term MC stand for that you referred to?
Alex: Master Electrician: Type of wire which is used in suspended ceiling applications.
Alex: Master Electrician: This is the one.