Which part of an NDC number identifies the package size of a drug?

The NDC is composed of 10 digits, which are divided into three segments: the labeler code, the product code, and the package code. While all digits serve specific roles in identifying the drug, it is the last two digits that directly specify the package size. Thus, stating "all of the digits" is too broad and inaccurate for this specific query.

The first five digits of the NDC represent the labeler code, which identifies the manufacturer or distributor of the drug. This segment does not pertain to the package size, making it an incorrect choice for identifying that specific aspect of the NDC.

The central four digits of the NDC indicate the product code, which identifies the specific drug formulation and strength. While important for product identification, this segment does not provide information about the package size, thereby rendering this choice incorrect.