单项选择题

According to the second paragraph, crows are poor subjects for field research for all the following reasons EXCEPT ______.

A．they can successfully avoid observers
B．they are hard to distinguish from one another
C．they can be quite aggressive
D．they are difficult to catch
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单项选择题
The locations of even the cemeteries indicate that ______.
A．middle class suburban areas are always, preferred
B．efforts have been made to make every visit convenient
C．people desire to put problems out of their sight
D．most people don't like the quietness of rural settings
单项选择题
In the last paragraph community based forms of treatment is used ______.
A．in contrast to treatment in specialized institutions
B．to show how efficient it is for mental illness and other diseases
C．to show how futile specialized treatment can be
D．as a synonym to treatment in specialized institutions
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