Correct Answer: Option B — The sum of digits is divisible by 9
Explanation:
A number is divisible by 9 when the sum of all its digits is divisible by 9. For example 729: 7+2+9=18 which is divisible by 9. Divisibility rules for 2 3 4 5 6 7 8 9 10 and 11 are important shortcuts saving significant time in competitive exam arithmetic and number theory questions.