What effects did the construction of the transcontinental railroad have on coast-to-coast communication? It made coast-to-coast communication instantaneous. It reduced coast-to-coast communication from about a week to about a day. It reduced coast-to-coast communication from about 180 days to about a week. It made coast-to-coast communication more complicated.

It reduced coast-to-coast communication from about 180 days to about a week. This question is mildly ambiguous due to the word "communication". Does it mean "Speed of sending a message?" or "Speed of moving a physical object?" Given the available options as answers, I will assume the meaning is "Speed of moving a physical object?" With that in mind, let's look at the available options and see what makes sense. It made coast-to-coast communication instantaneous. * Even modern jets can't travel from coast to coast instantaneously, so you wouldn't expect a train to do so either. So this choice is just plain silly and therefore wrong. It reduced coast-to-coast communication from about a week to about a day. * A stagecoach had an average speed of about 5 mph and covered 60 to 70 miles per day. So it's not going to go from coast to coast in only a week. And since that part of the answer is wrong, this choice is wrong. It reduced coast-to-coast communication from about 180 days to about a week. * The 180 day estimate is definitely doable. That's an average speed of about 17 miles per day which is a good speed for a person walking day to day. And that would be about 400 miles per day for the train. The numbers make sense and this is the correct answer. It made coast-to-coast communication more complicated. * Let's see. Buy a train ticket and possibly arrange for 6 layovers. Or plan a multiple month trip and possibly coordinate that effort without having any rapid means of communications? This option is just plain silly when you consider the logistics of traveling for several months vs traveling for a mere week. So this is a bad choice.