Question

what is one weakness of a federal system?
redundancy of government services
promotion of national unity
strong consistency among policies

Explanation:

In a federal system, there are multiple levels of government (federal, state, local etc.). This can lead to duplication of services as different levels may offer similar services, which is a weakness. Promotion of national unity and strong policy - consistency are generally seen as strengths, not weaknesses.

Answer:

redundancy of government services