Step 1: Recall the timeline of early amendments.
The 1st Amendment added the Ninth Schedule, and later amendments handled the voting age and reservations, so those can be set aside for the 7th Amendment.
Step 2: Recall the 7th Amendment specifically.
Passed in 1956, it reorganised the Indian states on a linguistic basis, replacing the old Part A, B, C, D classification.
Step 3: Confirm against the options.
This matches the reorganisation-related option directly.
\[ \boxed{\text{States Reorganisation on linguistic basis}} \]