What is the major observational difference between a Seyfert galaxy and a normal spiral galaxy?

Question

1. Normal spiral galaxies usually have shorter spiral arms.

2. Normal spiral galaxies never contain a supermassive black hole at their center.

3. The central region of a Seyfert galaxy is much brighter.

4. Seyfert galaxies don't contain any star formation.

Answer 1

It's number 3 -- I looked it up on Wikipedia.

Answer 2

You tell me; adding all this information about Galaxies tells me that you are testing us.

What about the quote:"No future in space without artificial gravity"?

A Star Trek fan.