At yesterday's networking event (www.meccanica-feminale.de) at the University of Stuttgart I met a nice young lady who is also learning Chinese. She mentioned the tongue twister "妈妈骂马 - māma mà mǎ" ("Mama scolds the horse"), which is of course a little hard to understand, out of context. Adding the yes/no question tag would even make it "妈妈骂马吗? - māma mà mǎ ma?" ("Does mama...?"). I hope you also have fun solving this sudoku.