What language to learn if I speak English, Chinese, Arabic?

I like to learn languages. I speak English Chinese and Arabic fluently. I want to learn a forth language "without any particular reasone behind that", and just need to hear some opinions from others on which language it should be, and why.

german?? it sounds elegant, besides, Germany is a Europe-dominating country - say economically.

Maybe Spanish. If you know Spanish in addition to English, Chinese, and Arabic, then you've essentially mastered the world's four dominant languages.

English = Dominant in North America and Europe (well, Germany is dominant economically in Europe, but the only language that can be understood by 95% of Europeans is English.)

Chinese = Dominant in Asia

Arabic = Dominant in Middle East and North Africa

Spanish = Dominant in Central and South America

You'll be on top of the world!!

English = not much use anymore.
Arabic = useful for blowing up stuff.
Spanish = good for siestas and socialising around plates of tapas.
Chinese = useful for confusing your interlocuters.
French = useful for communicating with your pets.

Polygolt: Thanks, you made me laugh after a long stressed day at work!

Si vous parlez le chinois, l'anglais et l'arabe couramment, la langue suivante pour vous doit être le français absolument. Parce que vous ne voudriez pas apprendre la meilleure langue sur la terre après toutes ces langues affreuses ?

Non, personne ne devrait apprendre une langue inutile et difficile comme le russe. Au lieu de cela vous devriez tous apprendre la plus belle langue sur la terre. Et on l'appelle 'le français'.

I say korean.

It is commonly recognised as the easiest language to be mastered. The character is appealing (i say). And consider the sad country had a beatiful
history.
May be you can learn that.

Or japanese which has similar grammar to korean

Or if you like literature,Russia ,French are all great