Is _Yr2006_Patient_Data a valid default variable name in SAS?

In SAS, variable names must adhere to specific rules to be considered valid. A valid variable name can start with a letter or an underscore and may be followed by any number of characters that includes letters, numbers, and underscores. Additionally, variable names must not exceed 32 characters in length.

The name "_Yr2006_Patient_Data" is valid because it begins with an underscore, which is acceptable in SAS. It also uses characters that are allowed in variable names and does not exceed the length limit. This means that "_Yr2006_Patient_Data" is compliant with naming conventions, making it a suitable variable name for use in SAS.

In contrast, other options would imply different restrictions or situations where the variable name might not be valid. However, considering the rules of SAS variable naming, the understanding that "_Yr2006_Patient_Data" meets all necessary criteria confirms that it is indeed a valid default variable name.