Final answer:
The [HoursWorked] field in the current database cannot be used in a calculated field.
Step-by-step explanation:
The correct answer is (c) [HoursWorked] (a field in the current database).
A calculated field in a database is a field that derives its value from an expression or formula rather than being stored directly as data. In this case, the field [HoursWorked] is an example of a calculated field because it is using a formula to calculate the number of hours worked.
The other options, (a) the number 12, (b) an asterisk (*), and (d) the % symbol can all be used in a calculated field. For example, you could use the number 12 in a formula to calculate a percentage of a value, or you could use an asterisk to multiply two values together.