BEIJING (AP) — China may ban Facebook, but not its co-founder Mark Zuckerberg, and he entertained an audience of students with a 30-minute chat in his recently learned Mandarin Chinese at a prestigious Beijing university. There was no explicit discussion of the ban or any Facebook effort to enter the China market during Wednesday's question-and-answer session at Tsinghua University. But Facebook CEO Zuckerberg noted during his talk that the social media giant already helps some Chinese companies gain customers abroad.Read more on NewsOK.com