Read the passage and choose the best answer to each of the following questions. There are many ways for dioxin, the toxic contaminant in Agent Orange, to enter the human body. To estimate the number of Vietnamese who have been impacted by Agent Orange, it is necessary to separate the exposure into three modalities. First is the past direct exposure to the poison in wartime. Second are those who may have been exposed to dioxin during or immediately following wartime through the contaminated soil ...

Read the passage and choose the best answer to each of the following questions.

There are many ways for dioxin, the toxic contaminant in Agent Orange, to enter the human body. To estimate the number of Vietnamese who have been impacted by Agent Orange, it is necessary to separate the exposure into three modalities. First is the past direct exposure to the poison in wartime. Second are those who may have been exposed to dioxin during or immediately following wartime through the contaminated soil or consumption of contaminated fish and animals. Third are those who are currently being exposed to the dioxin contaminant that remains in the soil. In addition, there are those in the second and even third generations who were not directly exposed but are potentially being impacted due to their parent’s or grandparent’s exposure. The population of South Viet Nam during the years of herbicide spraying was approximately 18 million. Jeanne stellman and her colleagues at Columbia University Mailman School of Public Health estimated that up to 4.5 million Vietnamese were living in the 3,181 villages that were directly in the spray paths and were potentially exposed to the dioxin. In addition, approximately a million more soldiers who were fighting in southern Viet Nam during the war were potentially exposed as they traveled through the sprayed areas. Unfortunately, there are not any firm figures for the number of adults who suffer from or have already died from illnesses associated with exposure to Agent Orange. We also do not know for sure how many children and youth have disabilities that may be attributed to their parents’ or grandparents’ exposure to the herbicides. (Excerpted from Agent Orange Record)

1. There are_________modalities of dioxin exposure.