【答案解析】The Decline of Smallpox
The graph shows the declining trend of the number of countries reporting cases of smallpox from 1964 to 1980.
The year 1964 is considered to be the worst year. In that year the number of countries reporting cases of smallpox was approximately 30. From that year on until 1977, there was a rapid decline in the number of countries reporting smallpox cases, with the actual number of reported cases dropping away to only two countries.
In the year between 1977~1978, there was a plateau in the number of reported cases, with the total remaining in two countries, and that number fell to zero in 1980.
The information presented on the graph tends to suggest that due both to improved methods of treating smallpox and to increased public awareness of the disease, thirty out of more than 200 countries world-wide have been successful in eliminating smallpox within a span of 16 years.