Mountain Biking - Wich one to choose from those 3?

Hello. I' m new here. It could be that im writing where i shouldnt but i'm not shore.
Wich bike is better? I know they are not very good, they are cheap, but...

http://www.1a.lt/tourism/dviraciai/details.php?id=50074512
http://www.1a.lt/tourism/dviraciai/details.php?id=50119205
http://www.dviratisplius.lt/index.php/sportiniai_dviraciai_cross_racing/stinger/4100_cross/1519

Sveikas! The Hexagon looks like it has a slightly better rear derailleur, but overall they all look pretty similar. None of them seem to have very robust wheels, so I wouldn't use them for any jumping or big bumps without planning on buying new wheels.

Sveikas :D xixi ...
Ok, thanks. That bike looks better for me too. I'll try to buy it. Thanks.

But also one person is offering me to buy from him this, also new:
http://www.positus.lt/lt/dviraciai/kelly-s-bicycles/mtb/2009-m-radius-orange
Just the model is of last year, but he said its better and it has shimano front star(correct?) block.

And also this one new:
http://img26.imageshack.us/img26/7806/getattachmentvqo.th.jpg
(http://img26.imageshack.us/i/getattachmentvqo.jpg/)http://img26.imageshack.us/img26/2281/getattachmentaj.th.jpg
(http://img26.imageshack.us/i/getattachmentaj.jpg/)http://img26.imageshack.us/img26/1831/getattachmentdsd.th.jpg (http://img26.imageshack.us/i/getattachmentdsd.jpg/)

The Radius Orange in the link seems to be better quality, BUT has a non-suspension fork. This will last longer and be more durable, but you will have to use your body position to "absorb" bumps such as tree roots on the trail. For riding on pavement and gravel, a non-suspension fork should be OK. Remember, suspension forks only became common about 10 years ago.

The white bike in the photos actually looks the best (but will need pedals! :) ). Having a disc brake in front is nice, since most of your braking force comes from the front wheel.

The "star blocks" are called the "crankset" (front, includes gears and crankarms) and "cassette" (rear, includes just the gears) here in the USA. Sheldon Brown did a lot of work on translating bicycle terms to different languages, but I don't think he got to Lithuanian. A partial list of some of his articles in some different languages is here: http://www.sheldonbrown.com/translations.html

Overall, if you end up riding many kilometers, plan on some parts wearing out and needing to be replaced. You can upgrade to better-quality parts if you want when you replace the old ones. The best way to have the bike work well is to learn how to do basic maintenance by yourself. www.parktool.com has a lot of repair/maintenance procedures (http://www.parktool.com/repair/bikemap.asp and click on the part of the bike you are interested in). www.bicycletutor.com has useful videos and information. Two good (English) books are:
http://www.amazon.com/Zinn-Art-Mountain-Bike-Maintenance/dp/193138259X/ref=ntt_at_ep_dpi_2
and
http://www.amazon.com/Bicycling-Complete-Bicycle-Maintenance-Repair/dp/1579548830/ref=ntt_at_ep_dpi_1

Good luck!