86. This passage is mainly concerned with ____.

1. the spread of the bird flu virus to mammals
2. the domestic and wild poultry population
3. H5N1 isolated only from chicken
4. a new virus strain jumping routinely from person to person

87. The fact that the H5N1 virus was isolated from apparently healthy ducks suggests that ____.

1. researchers worked really hard
2. ducks were inoculated with H5N1 vaccine
3. ducks might be a natural host of the virus
4. the virus made animals sicker than other viruses

88. We can infer from Paragraph 3 that ____.

1. the year in which the virus was isolated has nothing to do with the severity of illness
2. ducks are more likely to contract avian flu
3. accumulated mutations have occurred in the H5N1 virus
4. mice that are immune to the virus become sick

89. The findings show that the accumulated mutations ____.

1. have been adept at infecting mammals
2. may have contributed to the increased virulence of the virus
3. have led to the virus's DNA changes
4. require genetic analysis of the same samples

90. Koopman is convinced that human beings must learn to live with bird flu because ____.

1. study findings highlight the need for improved surveillance
2. wild animals are easy to cull
3. the disease could come back at any time
4. it is impossible to eliminate any natural host of the virus

(Reference keys.)