Hi @natluri,
We apologize for the error in the book. The correct answer is A, and not C. The DATA step uses the IN= data set option and the subsetting IF statements to exclude unmatched observations from the output data set.
We are currently updating our content updates page to reflect the necessary corrections in the Base Certification 4th edition. Once we have pushed the changes to the page, they will be available at the following link: Base Certification 4th Edition Content Updates Page
Best Regards, Samantha
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