What is the best to organize your url keyword structure?

[pigsinpink]

I'm working on an education site. The domain name for my site is a popular keyword.

i.e if my domain name = example.com

My Primary Keywords
a. classroom activities
b. kids classroom activities
c. classroom activities for adults
d. group classroom activities

Given the above example, what is the right way to structure the url so that it is optimized for the given keywords. Each primary keyword will have its own sub-topics.

1)example.com/kids-classroom-activities/kids-classroom-activities.html, example.com/kids-classroom-activities/page1.html
example.com/kids-classroom-activities/page2.html etc.

2)example.com/kids/index.html, ...page1.html etc.
example.com/adults/index.html, ...page1.html, page2 etc...
example.com/group/index.html etc...

3)example.com/kids/index.html
example.com/kids/page1.html
example.com/kids/page2.html

Thanks I appreciate your help,

[edited by: encyclo at 4:51 pm (utc) on May 13, 2007]
[edit reason] examplified, see terms of service [/edit]

[le_gber]

It really depend how your site's organised, but from what you said I would go:

example.com/classroom-activities/index.htm

example.com/classroom-activities/kids.htm

example.com/classroom-activities/adults.htm

example.com/classroom-activities/group.htm