The correct answer is: C. text box.
A calculated control is a control that displays the result of a formula. The formula can be based on the values of other controls on the form, or it can be a simple expression. To create a calculated control, you must use a text box control.
A command button is a control that executes a command when it is clicked. A combo box is a control that displays a list of items from which the user can select one. A list box is a control that displays a list of items from which the user can select one or more.
Here is an example of a formula that you could use in a calculated control:
=A1+B1
This formula would add the values in cells A1 and B1 and display the result in the calculated control.
Here is an example of a simple expression that you could use in a calculated control:
=1+2
This expression would add the numbers 1 and 2 and display the result in the calculated control.