Identify the correct form of reported speech of the following sentence among the following alternatives:
The teacher said, “Delhi became an Union Territory in 1956”

A

The teacher said that Delhi had been an union territory since 1956.

B

The teacher said that Delhi was to be an union territory in 1956.

C

The teacher said that Delhi had become an union territory in 1956.

D

The teacher said that Delhi became an union territory in 1956.