In the Thar region, the shifting sand dunes are locally referred to as "Dhrian". The term "Dhrian" is specific to the Thar region and is used by the local population to describe the phenomenon of moving sand dunes. These sand dunes are a distinctive feature of the Thar desert and are constantly shifting and changing shape due to wind and weather conditions. The word "Dhrian" is derived from the local language of the Thar region, and it signifies the movement and fluidity of the sand dunes. It is important to note that the other options listed in the question, namely "Daurs," "Dhoros," and "Dhaya," are not the correct terms used to describe the shifting sand dunes in the Thar region. Therefore, the correct answer is option 1, "Dhrian."