To answer this question, let's analyze the given code:
System.out.format("Pi is approximately %d.", Math.PI);
The System.out.format method is used to format and print a formatted string to the console. In this case, the string being printed is "Pi is approximately %d.".
The %d is a format specifier that is used for printing integers. However, Math.PI is a double value, not an integer.
Therefore, when this code is executed, it will throw a java.util.IllegalFormatConversionException at runtime because the format specifier %d is not compatible with the Math.PI value.
Hence, the correct answer is D) An exception is thrown at runtime.