The correct answer is C) 800,000 cubic meters.
The scale given is for the length, width or height of the model. In order to find the scale for the volume, we would cube this scale, since volume is a cubic measurement:
(1/200)³ = 1/8,000,000
Since the volume of the model is 0.1, we multiply this by 8,000,000 to find the volume of the actual dam:
0.1(8000000) = 800,000