上下层同时进行工作时，中间必须（）的防护盖板，工作人员必须戴（）。
参考答案：铺设严密牢固；安全帽
It is only when a football player has aged and been through many battles ________ he learns an important lesson: there is no “I” in “team”.
A．after
B．before
C．what
D．that
显影液中若忘了添加促进剂按正常显影条件冲洗出的胶卷将（）
