The graph gives the number of varicella (chicken pox) cases between 1972 and 2011. varicella is an infectious disease caused by a virus. the
disease causes rash, itching, and fever in patients. the varicella vaccine was introduced in 1995. what can you conclude about the vaccine?

a.
it was successful in eradicating chicken pox from the united states
b.
it had no effect on the rate of chicken pox cases in the united states
c.
it caused a 10% decrease in the number of chicken pox cases in the united states from 1995 to 2011
d.
it initially caused a large drop in chicken pox cases in the united states, and the rate continues to decrease

The answer is D. It initially caused a large drop in chicken pox cases in the United States, and the rate continues to decrease

Explanation:

Option A is incorrect, as we can see in the graph that the number of chickenpox cases never reached 0, even at its lowest point.

Option B is incorrect because, even though the rates had been decreasing before 1995, we can see a very rapid drop in the number of cases since 1995, leading to its lowest point in 2011.

Option C is incorrect . Based on the numbers on the graph, from 1995 to 2011, the number of chickenpox cases decreased from somewhere around 125,000 to somewhere around 10,000, meaning there were around 115,000 less cases, or 92% less cases.

the first phase of the government’s plan for settlement was building the transcontinental railroad. the railroad provided a way to bring settlers and manufactured goods west and ship their agricultural and mining produce east. the transcontinental railroad was an essential artery for rapid development of the frontier.

the second phase of the government’s plan was a liberal land distribution policy that made it possible for many people to homestead. with these two key elements—transportation and cheap land—the government rapidly achieved its goal of persuading people to move west, settle on farms, and push back the frontier.