The correct option is C 9
999 is divisible by 9.
On dividing 999 by 9, we get
9999=111.
999 is not divisible 7.
999 is not divisible by 4 as its last two digits 99 is not divisible by 4.
999 is not divisible by 6 as its last digit 9 is not divisible by 2, so its not divisible by 6 also.