Mount partition in Ubuntu

My harddisk has 2 partitions (C and D). Ubuntu only recognised C drive.

I opened the terminal and run:
sudo fdisk -l

I can see the D drive in the output. So, I have to mount it to Ubuntu.

sudo mount /dev/sda4 /mnt

Now I can access the D Drive from mnt folder.

To unmount, run:
sudo unmount /mnt