You deploy Windows 7 and several custom Internet Explorer add-ons to 1，000 client computers. Internet Explorer closes when users run a specific Web application.    You need to find out whether an add-on is the cause of the problem.   What should you do？（）

• A、Start Internet Explorer in No Add-ons mode.
• B、Reset all Internet Explorer security zones to the default levels.
• C、Use Group Policy to turn on Internet Explorer 7 Standards mode.
• D、Use Group Policy to disable the Programs tab in Internet Explorer for all client computers.