Most American colleges and universities use the grading system of A,B,C,D and F.

VOA: special.2009.03.05

So they began to call this A and this B and this C and this D and this E, this F, this G.

他们开始把这叫做A,B和C,这个是D,E,F,G

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These between B and C and E and F didn't get filled in because they were already just the smallest amount that they wanted to deal with, just half steps.

但是B和C,E和F之间并没有被填上,因为它们之间已经是最小的距离,只是个半音级,人们愿意摆弄的最小距离

耶鲁公开课 - 聆听音乐课程节选