不加填纸类有哪些？
参考答案：
抄造物理强度较高的纸类。如：纸袋纸、电缆纸等。
抄造具有良好吸收性能的纸类。如：羊皮原纸、钢纸原纸及生活用纸等。
— What's the matter with Andy ? He doesn't look very well.
— He has a headache because he ______ too long; he ought to have stopped reading.[ ]
A. had read
B. is reading
C. was reading
D. has been reading
凝聚剂和絮凝剂的添加顺序是（）。
A、没有先后顺序
B、先絮凝后凝聚
C、同时加入
D、先凝聚后絮凝
