设备加油“三过滤”原则（）、（）、（）
参考答案：进油桶过滤、进油壶过滤、进设备前过滤
计算下面各题，能简算的要简算．
（1）（6.8-5.4）×2.75-0.9
（2）3.8×5.6+4.4×3.8
（3）1.24×8.3+8.3×1.76
（4）88×0.25×9．
The Nile River ____ flood large areas but now the water ____ produce electricity. [ ]
A. used to; is used to
B. used to; used to
C. was used to; is used to
D. was used to; used to
