Before merging the main document with the data source, what should you do to make sure the merge fields, punctuation, and spacing appear as you intended?

A) Update fields.
B) Select recipients.
C) Preview the merge.
D) Specify a merge rule.

Previewing the merge allows you to see how the information from the data source will appear in the merged document, including the merge fields, punctuation, and spacing. This way, you can make any necessary adjustments before actually merging the main document with the data source. Updating fields, selecting recipients, and specifying merge rules are all important steps in the mail merge process, but they do not specifically address how to ensure that the merge fields, punctuation, and spacing appear as intended.