Question

in april 2009, a new strain of influenza a emerged. this strain, known as the swine flu, caused at least 95 deaths in over 40 different countries. the rapid spread of this disease can be attributed to
a. a lack of immunity within individuals and the lack of an effective vaccine
b. globalization and the ease with which one can travel from country to country
c. inadequate precautionary measures at the individual and community levels
d. all of these

Explanation:

个体缺乏免疫力且无有效疫苗，全球化使人员跨国流动便利，个人和社区层面预防措施不足，这些都可能导致疾病快速传播。

Answer:

D. all of these