I chose the third example.

"Las Vegas has too many people.(1.) There's not enough water in the desert to support more than a million people.(2.) And the infrastructure of the city can't handle more than a million people:(3.) The streets are overcrowded, and traffic is always congested; the schools are overcrowded, and new ones can't be built fast enough.(4.) We should stop migration to the city by tough zoning laws in the city and country.(5.)"

1. Is this in argument?
Yes

2. What is the conclusion?
We should stop migration to the city by tough zoning laws in the city and country. (4.)

3. Any additional premises needed?
There is too many people if Las Vegas can't handle more than a million people.

Las Vegas can't handle more than a million people if there isn't enough water, if the streets are overcrowded, and traffic is always congested, if the schools are overcrowed, and if new ones can't be build fast enough.

4. Identify any subargument:
Sentences 2-4
"There's not enough water in the desert to support more than a million people.(2.) And the infrastructure of the city can't handle more than a million people:(3.) The streets are overcrowded, and traffic is always congested; the schools are overcrowded, and new ones can't be built fast enough.(4.)"

5. Good Argument?
Yes it is a solid argument.

I actually enjoyed this exercise. It laid out the different parts of an argument and its claims. The one I chose was enjoyable because it is easy to relate to since I have family in Las Vegas.