单项选择题

H5N1 is a flu strain ______.

A．limited to Hong Kong
B．which first affected human beings in 1961
C．crossing species barriers
D．which was first isolated from American birds
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单项选择题
What should be done in order to stop the spread of bird flu
A．All infected fowls have to be slaughtered.
B．The government should isolate all the flu patients.
C．No fowl should be raised from then on.
D．Specialized hospitals should be established.
单项选择题
It has been discovered that______.
A．H5N1 does not transmit among human beings
B．bird flu spreads only among birds
C．H5N1 is a variant of flu virus
D．bird flu adapts easily to other species
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