The answer is D because the code fragment reads the content of the in.txt file and writes it to the out.txt file. The content of the in.txt file is "23456789". The code fragment uses a char array buffer of size 8 to read the content of the in.txt file. The while loop reads the content of the in.txt file and writes it to the out.txt file until the end of the file is reached. Therefore, the content of the out.txt file will be "0123456789".