The statement System.out.printf("%f", 123.456); is using the printf method, which is designed for formatted output in Java. The format specifier %f is utilized for floating-point numbers, which means it will display the number in decimal format.
By default, the %f format specifier prints the floating-point number with six digits after the decimal point. Therefore, when you pass 123.456 to this format specifier, the output will include three digits after the decimal that are provided (456) and three additional zeros to complete the six total digits after the decimal. Consequently, the output will be 123.456000.
This behavior is standardized in Java's printf functionality, ensuring consistent formatting across different floating-point outputs, which is why choice B is the correct answer.