Who was a french thinker who emphasized the use of mathematics as perhaps the most reliable way to acquire knowledge

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.

What was the national government’s biggest concern if facing a war, under the articles of confederation? the national government had no national military. the country had grown too large to defend with a small army. the states would not back the federal government. there was no way the states would pay for fighting a war.

Brainliesttt !me : ) what brought about the end of the soviet union?