How many Zonal Councils were set up vide Part-III of the States Re-org

How many Zonal Councils were set up vide Part-III of the States Re-organization Act, 1956 ?

Eight
Seven
Six
Five
This question was previously asked in
UPSC CDS-2 – 2019
Part III of the States Re-organization Act, 1956, originally established five Zonal Councils.
These five councils were the Northern, Central, Eastern, Western, and Southern Zonal Councils.
A sixth Zonal Council, the North-Eastern Zonal Council, was established later by the North Eastern Council Act, 1971, and includes the states of Assam, Arunachal Pradesh, Manipur, Meghalaya, Mizoram, Nagaland, Sikkim, and Tripura.