In Britain, One U

In Britain, one U.S.advertiser ran a campaign that centered on the slogan "You can use no finer napkin at your dinner table." In Britain, some people use the word "napkin" for the word "diapers." This would be an example of which of the following types of translation errors?

A) simple carelessness.
B) idioms.
C) local slang.
D) multiple-meaning words.
E) incorrect grammar.