To answer this question, we need to understand the syntax and behavior of the System.out.format() method.
In the given code snippet, System.out.format() is used to format output to the console. The format string "Pi is approximately %d." contains a placeholder %d, which is used to specify that a decimal integer value will be inserted at that position in the output.
However, the Math.PI constant in Java is a double value, not an integer. Therefore, when attempting to format the output using %d, a runtime exception will be thrown.
So, the correct answer is:
D. An exception is thrown at runtime