Final answer:
In SAS, you must use single quotation marks when you want an apostrophe to appear in a label.
Step-by-step explanation:
In SAS, you must use single quotation marks when you want an apostrophe to appear in a label. This is because double quotation marks are used to enclose the full label, while single quotation marks are used when you want to include an apostrophe within the label.
For example, if you want to create a label that says 'It's a beautiful day', you would need to use single quotation marks like this: label MyVar = 'It''s a beautiful day';
The correct answer to the question is option (a).