Which of the following is a standard numeric format in SAS?

The correct answer is that "w." represents a standard numeric format in SAS. This format allows you to define the width of the numeric value that will be displayed. When specifying the format, "w" indicates the total number of characters to be used to display the number, including any digits before and after a decimal point. This is crucial for controlling the appearance of numeric data in reports and output, ensuring consistency and clarity in data presentation.

In contrast, other options do not correctly represent standard numeric formats. For example, "$w." is a character format that is used for character data, specifically indicating that the variable is alphanumeric rather than numeric. The "n." format is not recognized as a standard numeric format in SAS; while "c." is also not a valid numeric format, it typically refers to a character format as well, which further distinguishes it from the numeric formats. Thus, "w." is the only appropriate choice for a numeric format in this context.