单项选择题 A user reports they can no longer change the web browser home page. Which of the following is MOSTlikely the problem? （）

单项选择题 A user states they receive a message Boot device not found half of the time they boot their system.Which of the following is the MOST likely cause? （）

单项选择题 A user reports that their system is starting to run slower, especially when opening large local files. The system has sufficient RAM for the users applications, but the hard drive seems to have higher than normal activity when opening large files. Which of the following would be the BEST tool to diagnose and troubleshoot this problem? （）