题目内容：
根据以下内容，回答题。This notice concerns all employees who use the conference rooms. Starting immediately, you will need to officially reserve any conference room you wish to use. Any reservations of longer than three consecutive hours will require the written approval of your department manager.
Reservation forms are available in the employee lounge. You must submit each form to your department secretary at least three business days in advance. If you need to cancel a meeting, please be sure to inform the secretary so that your reservation may be canceled as well. Any em-ployees using the conference rooms without proper authorization will be asked to leave.
Thank you in advance for your cooperation in this matter.
Joseph Mohammad
Assistant Director of Operations
From: Holly Graham <graham1917@nkkcompany.com>
To: Joseph Mohammad <mohahello@nkkcompany.com>
Subject: About the reservation of conference room
Dear Joseph,
I'm writing in response to your notice on reserving conference rooms. As a company sales manager, I have to say that my salespeople are not too happy with this sudden change in proce-dure.
Please keep in mind that they are often away on business trips or working on other assign-ments that keep them out of the office for long periods of time. They simply don't have the time to check the schedule and make reservation like on-site employees. If one of our clients shows up unexpectedly, it will be embarrassing for everyone if we don't have a conference room available.
I'd like you to consider making an amendment to the rule, allowing our sales force to reserve con-ference rooms at short notice. Thanks.
Holly Graham
What is the notice mainly about? A．Conference rooms may not be used for more than three hours
B．A meeting in the conference room has been canceled
C．Employees must reserve conference rooms in advance
D．Only department managers may use the conference rooms
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答案解析：