钳工锉齿纹的粗细是以每()mm内的锉纹来分的。
A.5
B.10
C.13
D.15
参考答案:B
Bill doesn't like the sunglasses in the ad because they can't _____ the sun well. [ ]
A. take out
B. keep out
C. clean out
D. look out
降低高炉炼铁工序能耗是当务之急。