XL Retail Sales,Inc

XL Retail Sales,Inc.,promises its head buyer Yancey and other salaried employees a bonus at the end of the year if management thinks that the circumstances indicate "a job well done." This promise is

A) enforce?able.
B) unenforce?able because it is not supported by consideration.
C) unenforce?able because the dollar amount is missing.
D) unenforce?able because the employees are paid salaries.