A number is formed by writing the same digit 8 times. That number is always divisible by?
Take an example of 11111111. This can be any of the 8 digits.
It would be divisible by 13 and 7 as if we could divide it into equal even groups of 3.
For 19, we need to divide it into even groups of 8. This is not true
This number is divisible by 11, where the rule of divisibility is sum of digits at odd places- sum of digits at even places.
Hence, Answer is none of these.