Which one of the following explains correctly?

• A. A number is divisible by 11, if the difference of the sum of the alternative digits is zero or a multiple of 11.
• B. A number is divisible by 11, if the last digit of that number is odd.
• C. If the sum of the digits of a given number is divisible by 11, then that number is divisible by 11.
• D. Given number is divisible by 11, if it is divisible by both 3 and 7.