Which of the Following Is a Difference Between PPOs and HMOs

Which of the following is a difference between PPOs and HMOs?

A) PPOs provide benefits at a reduced fee rather than on a prepaid basis as in HMOs.
B) HMO employees are not required to use only preselected plan service providers, as in PPOs.
C) PPOs are less expensive plans than HMOs if the employee goes out of the PPO network.
D) HMOs have more in common with traditional fee-for-service plans than do PPOs.
E) Unlike HMOs, payments to PPO physicians are made on a flat salary basis.