The correct answer is option 4: organization of labour under the factory system. During the early phase of the Industrial Revolution, which took place from approximately 1760 to 1850, the success of the revolution relied heavily on the organization of labor under the factory system. This system involved gathering large numbers of workers in centralized locations, such as factories, to operate machinery and carry out industrial tasks.

Option 1, machine power that replaced labor on a large scale, is also a significant factor in the Industrial Revolution. However, the organization of labor was necessary to effectively utilize machine power and ensure productivity.

Option 2, an elaborate road network for transportation of industrial products, is not the primary factor that determined the success of the Industrial Revolution. While transportation infrastructure did play a role, it was not the main driving force behind the revolution.

Option 3, a network of electric power stations, is not relevant to the early phase of the Industrial Revolution. This option refers to a later stage when electric power became significant in industrial processes.

Overall, the organization of labor under the factory system was crucial in the early phase of the Industrial Revolution, allowing for efficient utilization of machine power and driving the success of industrial production.