<span>C. Baby Boomers.
The period from 1946 to 1964 is known as the "baby boom" period in the United States. More babies were born in America than ever before in 1946, and the high birth rates continued for a number of years. Birth rates in the late 1940s and 1950s were much higher than they had been before, especially during the very low years of the Great Depression and World War II.
The birth rate in the US in 1935, in the midst of the Depression, was 18.7 births per 1,000 members of the population. At the peak of the Baby Boom in the 1950s, the birth rate reached over 25 births per 1,000 members of the population. In the present decade (the 2010s), the birth rate has dropped to around 12 births per 1,000 members of the population. </span>
Answer:
C. Doctors have been unable to develop a vaccine.
Explanation:
The Ice Age ended and the climate changed
