The correct answer is B. checkbox.
A checkbox is a type of control that allows the user to select or unselect an option. The user can select more than one option from a group of checkboxes.
A combo box is a type of control that allows the user to select an option from a list. The user can only select one option from a combo box.
A radio button is a type of control that allows the user to select one option from a group of options. The user can only select one option from a group of radio buttons.
A text box is a type of control that allows the user to enter text.
Here is a diagram that shows the different types of controls:
The checkbox is the only control that allows the user to select more than one option from a group.