Look at the graph below, which shows the population of the united states from 1790 to 1910

Your answer would be "from nearly 40 million in 1870 to nearly 80 million in 1900."

Or C. Hope this helps!!

monarchy doesn’t have to have the hereditary element. there have been elective monarchies in the past where you choose your king-for-life and when he dies elect someone else for the job.

i think they would live in caves or natural tunnels