Which letter is not pronounced in the words

“dumb”and“crumb”?

译句： “笨蛋”和“碎屑”这两个单词中的哪个字母不发音？ 

答案：  b

词汇：

dumb /dʌm/ adj. 哑的，愚蠢的

[近义词]：adj.  stupid

[反义词]：adj.  smart

[惯用语]： deaf and dumb 聋哑的

[例句]：

• It was dumb of you to say that.

  你说这种话太愚蠢了。

• She is very kind to the dumb children.

  她对哑童非常好。

crumb/krʌm/

n. 面包屑，碎屑，少许 

vt. 弄碎；捏碎

[近义词]：

n. small indefinite quantity，bit, bite

v. coat, surface, break up,

[惯用语]：

bread crumb 面包碎屑

biscuit crumbs 饼干碎屑

[例句]：

• Sheep's cheese, it's crumbly, it's salty.

  羊奶芝士易碎咸口。

• Don't forget the crumbs on the table.

  别忘了桌上的碎渣。

• He dropped crumbs of cake all over the table.

  他把蛋糕屑撒得满桌都是。