The NOBS= option in SAS is used to specify the number of observations in a data set. When you use this option in a SAS DATA step or when reading data from a data set, it allows you to determine how many rows (or records) exist in the specified data set without actually reading through all the data. This can be particularly useful for looping or conditional processing where knowing the total number of observations can inform how many iterations to perform or whether certain conditions are met.
In this context, it is clear that the other options relate to different aspects of working with data in SAS. The number of variables in a data set pertains to structure and not observation counts. The name of the data set is directly referenced without needing a specific option to denote it and the storage length of a variable describes how much memory is allocated for that variable, which is unrelated to the concept of counting observations. Therefore, understanding that NOBS= focuses specifically on the count of observations highlights why this choice is the accurate selection in relation to the functionality of SAS programming.