You need to identify potential security threats. Which of the following security breaches might occur under the current IT and security practices？（Choose all that apply）（）
- AA virus that infects an IT administrator’s client computer could gain domain administrator privileges
- BCouriers could gain access to domain administrator privileges
- CBusiness office staff could discover couriers’ passwords and use them to access couriers’ information
- DAll users could use their user accounts to gain the ability to install untested security patches on their client computer