Final answer:
To delete the 'FirstName' field from a query in Design view, you should select the field and press the Delete key on the keyboard.
Step-by-step explanation:
To delete a field from a query in Design view in a database management system like Microsoft Access, you can use several methods. However, option A) 'Right-click on the "FirstName" field and select "Delete"' and option D) 'Click on the "FirstName" field and choose "Remove" from the toolbar.'
do not typically apply since these are not standard ways to remove fields in query design. The correct way to delete the field is by using option C): Press the Delete key after selecting the "FirstName" field. Here are the steps:
Select the "FirstName" field in the Query Design Grid.
Press the Delete key on your keyboard.
The field will be removed from the query grid, and thus not be included in the query results once you run it.