单选题：In our experiment of adding a new file system, we use the follow

In our experiment of adding a new file system, we use the following scripts to test our new file system.
```
1. dd if=/dev/zero of=myfs bs=2M count=1
2. /sbin/mkfs.ext2 myfs
3. ./changeMN myfs
4. mount –t myext2 –o loop ./fs.new /mnt
5. mount
6. umount /mnt
7. mount –t ext2 –o loop ./fs.new /mnt
```
What is the command in line 1 used to?@[D](1)
A. create a 2M file in device /dev/zero
B. create a 2M file myfs with all 1s
C. create a file myfs with block size 2M in device /dev/zero
D. create a file myfs with all zeros and its block size is 2M





A.create a 2M file in device /dev/zero
B.create a 2M file myfs with all 1s
C.create a file myfs with block size 2M in device /dev/zero
D.create a file myfs with all zeros and its block size is 2M


答案：D