Which answer best completes the following sentence?

Two advantages of a unitary government are that it ______ and ______.
Select one:
a. citizens can participate at multiple levels of government; the national government may be too weak to provide services
b. citizens can participate at multiple levels of government; overlapping national and local services may be wasteful
c. power is concentrated on the national level; the national government may not be aware of local issues
d. power is concentrated at the local level; the local government may not be able to cooperate on national issues