Help me with this Question I am giving 15 Points

Rachel carson 1962 silent spring was a groundbreaking work regarding what topic

What was a major cause of world war i?

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.