During the earliest period of industrialization in Britain, steam engines were more expensive to build and operate than either windmills or water mills, the other practicable sources of power for factories. Yet despite their significant cost disadvantages, steam-powered factories were built in large numbers well before technical improvements brought their cost down. Furthermore, they were built even in regions where geographical conditions permitted the construction of wind-and water-powered factories close to major markets. Which of the following, if true, most helps to explain the proliferation of steam-powered factories during the earliest period of industrialization in Britain? ['In Britain, the number of sites where a wind-or water-powered factory could be built was insufficient to provide for all of the demand for factory-produced goods at the time.', 'It was both difficult and expensive to convert a factory from wind power or water power to steam power.', 'Unlike wind-or water-powered factories, steam-powered factories were fueled with coal, which sometimes had to be transported significant distances from the mine to the site of the factory.', 'In many areas of Britain, there were fewer steam-powered factories than wind-or water-powered factories in the earliest period of industrialization.']