The correct answer is C. abs().
The abs() function returns the absolute value of a number. The absolute value of a number is its distance from zero on the number line. For example, the absolute value of 5 is 5, and the absolute value of -5 is also 5.
The sqrt() function returns the square root of a number. The square root of a number is a number that, when multiplied by itself, equals the original number. For example, the square root of 9 is 3, because 3 times 3 equals 9.
The round() function rounds a number to the nearest integer. For example, the round() function rounds 3.5 to 4, and the round() function rounds 2.5 to 3.
The len() function returns the length of a string. The length of a string is the number of characters in the string. For example, the length of the string “Hello” is 5, because the string contains 5 characters.