What did the sign say? 那标牌上写的什么字?

In the doctor's waiting room I saw a mother helping her little boy sound out the words on a sign. Finally he mastered it and his mom cheered, “That's great! Now sit there. I'll be back in 15 minutes.” What did the sign say? “Children must not be left unattended.”

在医生的候诊室里我看到一个母亲正在教她的小男孩读一个标牌上的字。最后，小男孩学会了。母亲高兴地说：“太棒了!现在你坐到那儿，我过15分钟回来。”那标牌上写的什么字?“孩童不可无人照看。”