The answer that you're seeking is, "Trains from different rail lines could use each other’s tracks." The standardization of rails allowed trains to use eachothers tracks and increase speed and efficieny in deliveries. Hope I helped!
Answer:
Income tax , property tax and sales tax
I think it's D. after conquering southern China, he ruled over the largest land empire in history.
It’s C because the quantity demanded wasn’t met.
