Why did the transcontinental railroad lead to the end of the pioneer era

Immigration to western parts of the US became easier, rails that connected the populated East and low population West meant the West could now receive more from the East. Because of this, settling down in the West became easier. More farms popped up and cities began forming as living there was now possible.

Explanation:

answer; (d) none of the above;

c

explanation: because you need to reduce the pollution on land,the exhaust fumes will stop,and stop it in water,the oil that is in the oceanharms the fish   sorry if you   have been waiting long