阅读理解。
Honeybees are disappearing for unknown reasons around the United States. Last winter, bees disappeared
from 23 percent of American beekeeping businesses. Causes of the occurrence, however, have remained a
puzzle.
Now, scientists from several universities and the United States Department of Agriculture say they have a
possible explanation for the bee decline (数量下降). It is a little known virus called Israeli acute-paralysis virus
(IAPV).The virus kills bees. Researchers in Israel first described it in 2004, but until now, bee experts haven't
paid much attention to it.
When trying to find out why the bees were disappearing, a research team at Columbia University studied
bee communities, some with and others without decline. The research turned up large numbers of two types
of fungi (真菌) once believed of causing the bee decline. The research results, however, showed that the
fungi were almost as common in communities without a decline as they were in communities with a decline.
The research concluded that the two fungi probably weren't the cause.
Studies of the presence of IAPV, however, showed more interesting information. In those studies, done
by a team at Pennsylvania State University in University Park, the virus showed up in 83 percent of samples
from communities with symptoms. Only five percent of samples from symptomless communities had it.
Scientists still don't know whether IAPV can single-handedly cause the bee decline. They believe that even
if the virus is making communities sick, it could have a partner in crime. It's possible, for instance, that insects
or chemicals in the environment weaken bees, making them more likely to catch IAPV.
Scientists are still trying to figure out how IAPV came to the United States. The United States now allows
bee products to be imported from Canada, Australia, and New Zealand. If it turns out that this trade is
spreading disease, the rules might eventually change.
1. According to the passage, IAPV is a virus that _____. [ ]
A. is difficult to be killed
B. is spread by a kind of fungi
C. is still not fully understood
D. is caused by the imported bee products
2. From the third and fourth paragraphs, we know researchers draw their conclusion through _____. [ ]
A. calculating
B. comparing
C. examining
D. investigating
3. The underlined sentence in the fifth paragraph probably means _____. [ ]
A. the virus is not only among insects
B. the virus could also cause other damages
C. the virus is not the only cause for the bee decline
D. the virus may be caused by the polluted environment
4. What is the best title for the passage? [ ]
A. Symptoms of LAPV
B. A Virus-IAPV
C. Fungi and Virus
D. Disappearing Bees
