装置内未经批准，一律不准使用蒸汽烧水、蒸饭。(安全与环保知识)
参考答案：对
黄柏粉末可见（）
A.黄色石细胞
B.晶纤维
C.草酸钙方晶
D.黏液细胞
E.具缘纹孔导管
Nearly three months had gone by ______ the seriously injured girl showed a slight sign of recovery.
A．until
B．after
C．since
D．before
