Which second foreign language should I choose?

French...it's the language of love!

Spanish, as it is the second language of the United States.

If you intend to remain in or direct your business interests toward North America, then i would advise Spanish, because it is so widely spoken in both North and South America. If you intended to go into a line of business which puts you in touch with central Africa, then I would advise French. Russian might be useful, if your future interests lie in central Eur-Asia. Most well-educated people in Central Asia north of the Hindu-Dush learned to speak Russian as children, for however much they may have despised their masters.

Good luck in your studies.

Thank you for your suggestions : )
It seems that Spanish is a better choice. But I never touched Spanish before. I learned French for about 2 month, one year ago. In my heart I prefer French. But it looks like that French is not that useful in American. So I haven't made the decision yet.
Another thing is that I can't find some person to learn the language together. It is really hard to stick to learn by yourself,especially for a foreign language.