There is lots of good information being offered on this thread. I will add that our team uses C++ both because our programming mentor (me) has expertise in C++. But I also chose C++ because it is very similar syntactically to Java but gives the programming a few more tricks and improved run-time performance. The other key element to the decision was that many high schools teach Java (often since the AP Programming test is in Java). C++ is not a huge leap from Java so it is a great opportunity to help these students take that next step and learn another language.
I would also offer this link (
http://iel.ucdavis.edu/publication/WhyC.html) to a paper from a few years back that provides some insight into what languages are used in industry.