Which of the following is a feature of the F.E.R.S, for U.S. Civil Service employees?

a. an employee is eligible to retire at age 55 with 30 years of service. b. an employee is eligible to retire at the age 57 with 30 years of service c. the plan exclusively uses a defined benefit approach d. the plan features a survivors benefit of up to 55% of the initial unreduced social security benefit