例句：

　　Dust masks are graded according to the protection they offer

　　防塵口罩根據(jù)它們的防護(hù)效果分等級。

　　Milk is sold in grades.

　　牛奶是分等級出售的'。

　　Why get upset just because you got one bad grade?

　　何必因?yàn)橐淮纬煽儾缓镁拖氩婚_呢？

　　All the materials used were of the highest grade.

　　使用的材料全是優(yōu)質(zhì)品。

　　You get an A grade for scores of 75 and over.

　　75分及75以上的分?jǐn)?shù)就是優(yōu)等。