The Next "It" Language

After English, what is the world's "it" language? I'd be hard-pressed to argue that it isn't Spanish, Mandarin Chinese, or Arabic, and I'd personally lean towards Mandarin just because China is making such strides economically and most likely will continue to do so. I have at least a tiny bit of familiarity with all of these languages (meaning I know at least a word or two and have some idea of the grammatical structure), and I think an exploration of the pros and cons of studying each one for those who want to increase their linguistic knowledge is in order in the next few posts. I'll start with Spanish.