How did scientists apply albert einstein's equation e = mc2? a) to create functional spacecraft b) to develop nuclear power c) to change the law of gravity d) to improve public hygiene

How did the completion of the transcontinental railroad change the lives of american citizens? a-it increased the wealth of all americans and enabled them to travel more.b-it made cross-country travel too expensive for ordinary americans.c-it decreased the safety of americans who moved to settle the plains.d-it shortened travel time between the east and west for all americans.