Explanation:

- Option 1: Planning Commission

This body no longer exists (replaced by NITI Aayog). When it did exist, Chief Ministers were not ex-officio members.

- Option 2: National Development Council

Correct Answer: All Chief Ministers of the States are ex-officio members of the National Development Council, which was set up to strengthen and mobilize the effort and resources of the nation in support of the Plan.

- Option 3: Inter State Council

The Council includes Chief Ministers as members, but not strictly ex-officio for all states as per the statutory provisions.

- Option 4: Finance Commission

Chief Ministers are not members, ex-officio or otherwise, of the Finance Commission.

Correct Option: Option 2, National Development Council