判断下列命题的真假，并说明理由。　　（1）如果（A∨C）⇔（B∨C），则A⇔B；　　（2）如果（A∧C）⇔（B∧C），则A⇔B；　　（3）如果﹁A⇔﹁B，则A⇔B。

Given that the current directory is empty， and that the user has read and write privileges to the currentdirectory， and the following： Which statement is true？（）

A、 Compilation fails.

B、 Nothing is added to the file system.

C、 Only a new file is created on the file system.

D、 Only a new directory is created on the file system.

E、 Both a new file and a new directory are created on the file system.

A laser printer displays ‘perform user maintenance’. The manufacturer’s information was not available when the user performed the maintenance, and the laser printer continues to display the maintenance code. Which of the following items needs to be performed?（）

A、The printer needs to be sent to the manufacturer for maintenance.

B、The printer’s firmware needs to be updated.

C、A printer system reset must be performed.

D、The maintenance page counter must be reset.

Which of the following system utilities would be used to change a drive type from dynamic tobasic?（）

A、System Partition Manager

B、NTBACKUP

C、Device Manager

D、Disk Management

6阶有限群的任何子群一定不是（　　）阶。

A、2

B、3

C、4

D、6

[AddJump]：增加跳线。同时按下J键和Ctrl键也可以实现同样功能。

A、对

B、错