Answer: The correct options is (D) 128 units³.
Step-by-step explanation: We are given to find the volume of the regular pyramid shown in the figure.
The VOLUME of a regular pyramid with base area 'b' square units and height 'h' units is given by

In the given figure, we have
base area = 8 × 8 = 64 units² and height, h = 6 units.
Therefore, the volume of the regular pyramid is

Thus, the required volume is 128 units³.
Option (D) is correct.