Which of the following statements about the commercial umbrella liability policies is false?
a) they provide coverage above the limits of underlying policies.
b) losses that are excluded by the underlying policy but covered by the umbrella are subject to the umbrella's retention limit.
c) if the insured fails to keep the underlying coverage in force, the umbrella policy will not cover the amount of loss that would have been paid by the underlying policy.
d) they are written only for commercial risks.