super noob question

hey im trying to get into the game and im playing the demo now and ill be picking up the trilogy tommorow and I have a question...is it possible to only have one class? Im at the quest A Second Profession and im wondering can i advance the main quest without picking a second profession?

To some point you don't need a secondary profession, but eventually you will have to get one.

Also, Just because you HAVE a secondary profession, doesn't mean you have to USE any skills from that Secondary Profession.

If you make a character in Nightfall, you can get a ferry to one of the other campaigns before you have to choose your secondary in Nightfall, and level up from there with only your primary. But as Kosar said, theres really no reason not to grab a secondary profession. You don't actually have to use it.

Just in case you were wanting to retain your options until you knew more about the game....

GW is really flexible about secondary profs and attributes...

you can switch around your atts in town and later in the game you get the option to change your secondary at will.

To advance past the beginner area in the Prophecies campaign (which is the trial campaign) you will need to choose a secondary profession. As others said you don't need to use any skills from that profession if you choose not to and you can later in the game use other secondaries.

You can read the stickied basics threads in our Campfire section profession subforums to get an idea of which secondaries will be of more use to your primary profession.

You will need to choose one. but you do not need to use the skills in them. Most players will choose something that goes well with their main class and use a little of the secondaries. When you get further, you will be able to change them as well. (Far, far, far away for Prophecies, extremely quick for Fractions and okay, not that far for Nightfall)

Yes, it is sort of possible by doing certain "tricks", but as has been said, there's no reason to do it. You don't need to use any of the skills of your secondary and you don't need to put any points in any secondary attribute.
The simplest thing, at the start, is to take /Monk as a secondary. That gives you access to a better rez skill than a signet, and perhaps a self-heal if you have a skill slot available and a few "leftover" points to put into it.
Later in the game you will be able to change your secondary to whatever you want, as often as you want.