What action should be taken to add a subform control to a form?

To add a subform control to a form in Access, the correct approach involves utilizing the Controls group on the Design tab. When the user selects 'Subform/Subreport' from this group, they are provided with the capability to embed a subform or subreport directly within the parent form. This method allows for the seamless integration of related data, which can enhance the functionality and usability of the form by displaying additional details without navigating to a separate form.

Selecting the correct control from the Controls group is essential because it ensures that the subform behaves as intended within the parent form, maintaining the relationships and data integrity associated with the subform. This approach simplifies the design process, as the user can seamlessly drag and drop the subform onto the form layout, adjusting its size and placement as needed.

Other options do not conform to the standard process for adding a subform. For example, inserting a subform by clicking on an existing field or right-clicking on the form may not provide the necessary features and tools for connecting the subform to its data source as effectively as using the designated Controls group. Accessing the Property Sheet is related to modifying existing properties of the form but does not directly facilitate the addition of new controls like a subform.