单选题：The following question are related to the following shell script

The following question are related to the following shell script (with line numbers for easy reference)
```
1). dd if=/dev/zero of=myfs bs=1M count=2
2). mkfs.ext2 myfs
3). changeMN myfs #to change the manic number to the right value
4). mount –t myext2 –o loop myfs /mnt
5). mount
6). umount /mnt
7). mount –t ext2 –o loop myfs /mnt
```
The effect of the command in line 1 is __. @[C](1)
A. to create a new device file named myfs
A. to copy the file /dev/zero with size 2M bytes to the file myfs
B. to set the contents of the first 2M bytes of the file myfs to all-zero
C. to create an all-zero file myfs of size 1M bytes





A.to create a new device file named myfs
B.to copy the file /dev/zero with size 2M bytes to the file myfs
C.to set the contents of the first 2M bytes of the file myfs to all-zero
D.to create an all-zero file myfs of size 1M bytes


答案：C