The correct answer is C. Input Mask.
An input mask is a field property that displays a model or pattern for entering data. It helps to ensure that data is entered correctly and in the correct format. For example, an input mask for a phone number might require that the user enter the area code, followed by three digits, followed by three more digits.
The other options are incorrect because:
- Field Size is a field property that specifies the maximum number of characters that can be entered into a field.
- Format is a field property that specifies how data is displayed in a field.
- Validation Rule is a field property that specifies rules that must be met when data is entered into a field.