单词s--and-f-
Across the counted states boys have never been in more trouble: They earn 70 percent of the D "s and F"s that teachers dole out.
在全美国，男孩从来没有过这么麻烦：在为数不多的获得D级和F级分数的学生中，他们占70%。
He graduated from White Pine High School in Ely 1963, getting mostly C"s, D"s and F"s.
1963年他毕业于伊利的白松高中，大部分课程得分是C、D和F。
And lastly, the compensation system received 79 percent D"s and F"s.
最差一项是薪酬体系，D和F的评级占79%。