New World Epidemics

    A huge loss of life resulted from the introduction of Old World diseases into the Americas in the early sixteenth century. The inhabitants of the Americas were separated from Asia, Africa, and Europe by rising oceans following the Ice Ages, and, as a result, they were isolated by means of this watery barrier from numerous virulent epidemic diseases that had developed across the ocean, such as measles, smallpox, pneumonia, and malaria. Pre-Columbian Americans had a relatively disease-free environment but also lacked the antibodies needed to protect them from bacteria and viruses brought to America by European explorers and colonists. A devastating outbreak of disease the strikes for the first time against a completely unprotected population is known as a virgin soil epidemic. Virgin soil epidemics contributed to an unbelievable decline in the population of native inhabitants of the Americas, one that has been estimated at as much as an 80 percent decrease of the native population in the centuries following the arrival of Europeans in the Americas.

10. The word they in the passage refers to

   (A) the inhabitants

   (B) epidemic diseases

   (C) rising oceans

   (D) the Ice Ages

11. The word that in the passage refers to

   (A) a disease-free environment

   (B) this watery barrier

   (C) virulent epidemic diseases

   (D) the ocean

12. The world them in the passage refers to

   (A) pre-Columbian Americans

   (B) the antibodies

   (C) bacteria and viruses

   (D) European explorers and colonists

13. The word one in the passage refers to

   (A) a virgin soil epidemic

   (B) an unbelievable decline

   (C) the population of native inhabitants

   (D) the arrival of Europeans

参考答案：

10-13：A、C、A、B