Answer:
Field names should start with a letter is not a rule for data source for a mail merge.
Explanation:
The best Microsoft tool to use for a data source in a Microsoft mail merge is Excel spreadsheet, a data source for a mail merge can also be a database or a table .
Mail merge is the merging/combining of mail and letters or labels meant for mailing in mass from a form letter. this simply means that Microsoft word documents can take in content from databases, spreadsheet.
A data source is used to define the connection between a data from its source to its recipient. it is the name used when querying a data .
every other options given is a rule because it makes the field name unique and easy to query the data source as well
