Which option is the correct way to comment out a line of code in SAS?

In SAS, the correct way to comment out a line of code is to use the syntax that begins and ends with slashes and asterisks, like in the example provided. This means that any text placed between /* and */ will be treated as a comment and not executed as part of the code. This style allows for multi-line comments as well, which is particularly useful for documenting larger sections of code or for temporarily disabling parts of it during testing or debugging.

The other options do not conform to SAS syntax. The usage of double dashes (--) for comments is characteristic of SQL and some other programming languages but is not valid in SAS. The use of double slashes (//) is also not applicable in SAS code; this style is more common in languages like C++ or Java for single-line comments. Lastly, while asterisks and semicolons can denote comments in SAS, the structure "** This is a comment **;" does not follow the correct commenting format; the comment should instead be enclosed within the proper delimiters. Thus, the use of /* comments */ is the standard method in SAS for effectively commenting out code.