In late September, Kimberly Williams-Guillen, a professor at the University of Washington Bothell, r

In late September, Kimberly Williams-Guillen, a professor at the University of Washington Bothell, received a report that a handful of howler monkeys had been found dead in Nicaragua. Strangely, the monkeys showed no signs of disease. Over the next couple of months, the reports really started to flood in. When it became clear that this was not just an isolated(独的)incident, Williams-Guillen boarded a plane to Nicaragua to see for herself.
Williams-Guillen speculates that the deaths may be linked to the drought that has struck Nicaragua this year. “The deaths are concentrated in the areas worst hit by drought and the trees are just bare—there’s hardly a leaf to be eaten,” she says.
Kenneth Glander of Duke University agrees that limited food availability is likely a contributing factor. Rather, the lack of food may drive the monkeys to consume plants with high levels of certain toxins(毒素)that aren’t part of their normal diet.
Another possible cause for the howler monkey die-offs is disease. Although Nicaragua is currently believed to be free of yellow fever, Glander points out that outbreaks of the viral disease ruined howler monkey populations in the late 1940s and into the 1950s. Some researchers even think that yellow fever may be a cause of the relatively low genetic American howler monkeys.
Wiliams Guillen thinks that disease is an unlikely cause of the recent monkey deaths, however. While she and her colleagues are still waiting to export blood and tissue samples to U.S. labs for further analysis, she notes that a Nicaraguan researcher has experimented on some of the samples. And, so far, none have tested positive for yellow fever, Zika, chi-kungunya, or dengue viruses.
For now, however, the cause of the recent howler monkey deaths remains a mystery. Williams-Guillen suspects that no one’s hypothesis(假说)will be correct. “There’re probably many factors,” she says. “Animals that might have had some clinical or secondary infections that normally aren’t that problematic... got into a situation where they were extremely food-and water-stressed, and that might have been enough to cause them to die.”
12．According to Paragraph 1, an early consideration regarding the howler monkey deaths was whether they ______.
A．were simply random occurrences
B．affected howler monkeys of all ages
C．were related to the environment in Nicaragua
D．could be prevented through food distribution
13．What does the underlined word “speculates” in Paragraph 2 probably mean?
A．Denies. B．Guesses.
C．Bothers. D．Declares.
14．What does Paragraph 5 mainly aim to do?
A．Define Williams-Guillen’s method.
B．Stress Williams-Guillen’s assumptions.
C．Provide Williams-Guillen’s perspective.
D．Demonstrate Williams-Guillen’s expertise.
15．What can we infer from the text about the death of howler monkeys?
A．William-Guillen used lab tests to show its influence.
B．It really resulted from limited food availability.
C．No final conclusion has been reached about it.