单选题 . 
    The White House is the most visited residence in the world. Tours may be scheduled through our Washington D. C. office. Due to security and scheduling procedures, there are a few things you should know before requesting a tour:
    ·Only groups of 10 or more may request a tour.
    ·Requests must be submitted with a minimum of one month's advance notice from the date of the tour. Notice of whether your application is accepted will be given 10 days prior to the date requested. All tours, even after they have been confirmed, are subject to cancellation due to security interests.
    ·Tours are only conducted Tuesday through Saturday from 7:30 am to 11:30 am.
    To process your request for a tour, please contact our Washington office at (202) 224-5521.1.  This notice is to provide information about ______.