Special kinds of cotton that grow fibers of green or brown have been around since the 1930s but only recently became commercially feasible when a long-fibered variety that can be spun by machine was finally bred. Since the cotton need not be dyed, processing plants avoid the expense of dyeing and the ecological hazards of getting rid of leftover dye and by-products. Which one of the following can be properly inferred from the passage? ['Green and brown cottons that can be spun only by hand are not commercially viable.', 'Hand-spun cotton is more ecologically safe than machine-spun cotton.', 'Short-fibered regular cottons are economically competitive with synthetic fabrics.', 'Garments made of green and brown cottons are less expensive than garments made of regular cotton.']