Did you get . . . . . . . . birthday card that I sent you? A. a B. an C. the D. no article

The correct answer is D. no article.

The word “birthday” is a common noun, which means that it does not refer to a specific birthday card. Therefore, we do not need to use an article.

If we were to use an article, it would imply that we are referring

However, in this case, we are simply asking if the person received any birthday card. Therefore, we do not need to use an article.