D) Scale of the market
Technological progress refers to the process of invention, innovation and diffusion. In other words we can say, that technological progress leads to a better utilization of the given amount of resources enabling firms to produce more and more goods with the same amount of resources.
Thus, innovation, scientific research and education are all part of the technological progress but they are not caused due to technological progress, they only lead to technological progress.
While, Scale of the market is the cause of the technological progress.
The answer would be letter D.