The 'b' had been wrongly written as a 'd'.

b错写成d了。

《牛津词典》

In the A, B, C, D and F grading system, the first four letters are typically considered passing grades.

在 A、B、C、D 和 F 评分体系中，前四个字母通常被认为是及格。

youdao

After you hear a question, you must choose the best answer from the four choices marked A, B, C and D.

听到问题后，必须从A、B、C、D四个选项中选出最佳选项。

youdao

An A is worth four points, a B three points, a C two points and a D one point.

VOA: special.2009.03.05

I quote in here a guy who croaks before this course starts, Jean Bodin, B-O-D-I-N.

在这儿我引用一位逝者提出的观点,金博丹

耶鲁公开课 - 欧洲文明课程节选

Again I should have said first, index 0, the first one. I can similarly go in and say I'd like all the things between index 2 and index 4. And again, remember what a b c that does. Index 2 says start a 0. 1, 2. So a, b, c.

我还是要说一遍，索引为0的元素，是第一个元素，我可以要求返回索引,2和4之前的所有元素，请记住2,是从0开始的,那么0，1，2对应的是。

麻省理工公开课 - 计算机科学及编程导论课程节选

Nearby, d.b.a serves up some of the most diverse musical offerings in town and has a great beer menu to boot.

BBC: The other New Orleans soundtrack

Oh, we almost forgot -- they've boosted out the keyboard in favor of a more useful D-pad and A, B, X, Y button formation -- which is, needless to say, awesome for playing awesome games.

ENGADGET: Seabright PC430 "micro PC" spurns keyboard, not coolness

It is the phenomenon whereby we assume that because people are good at doing A they will be good at doing B, C and D (or the reverse because they are bad at doing A they will be bad at doing B, C and D).

ECONOMIST: Idea