I tried the command you mentioned. The following is the output. I tried hda5 , hda6 and hda7.
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[root@h157n2fls301o1037 root]# mount -t ntfs /dev/hda6 /mnt/D
mount: /dev/hda6 already mounted or /mnt/D busy

[root@h157n2fls301o1037 root]# mount -t ntfs /dev/hda5 /mnt/D
mount: /dev/hda5 already mounted or /mnt/D busy

[root@h157n2fls301o1037 root]# mount -t ntfs /dev/hda7 /mnt/D
mount: /dev/hda7 already mounted or /mnt/D busy

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[root@h157n2fls301o1037 root]# mount -t vfat /dev/hda5 /mnt/D
mount: /dev/hda5 already mounted or /mnt/D busy
Here I wrote the vfat instead of ntfs.
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[root@h157n2fls301o1037 root]# mount -t vfat /dev/hda6 /mnt/D
[root@h157n2fls301o1037 root]# ls
drakx/ tmp/
Here I wrote vfat with hda6. It worked. The output is strange.
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[root@h157n2fls301o1037 root]# mount -t vfat /dev/hda4 /mnt/D
mount: special device /dev/hda4 does not exist
Here I wrote vfat with hda4. The answer is different.
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[root@h157n2fls301o1037 root]# mount -t vfat /dev/hda3 /mnt/D
[root@h157n2fls301o1037 root]# ls
drakx/ tmp/

Here I wrote vfat with hda3. This output is strange too.
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[root@h157n2fls301o1037 root]# mount -t ntfs /dev/hda3 /mnt/D
mount: /dev/hda3 already mounted or /mnt/D busy
mount: according to mtab, /dev/ide/host0/bus0/target0/lun0/part6 is already mounted on /mnt/D

Here I wrote ntfs with hda3. What is the output?
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I can't fathom the above outputs. I mean three partitions can't be busy at one and the same time.
So please help me. I deeply appreciate your help.

Please tell me what to do next.

Please read my questions and help me. I am in a big trouble. I am patiently waiting for your help.

So please help me.