题目内容：
Influenza(流感)Influenza has been with us a long time. According to some Greek writers(51) medical history, the outbreak of 412 B.C. was of influenza. The same has been suggested of the sickness (52) swept through the Greek army attacking Syracuse in 395 B.C. Influenza is a disease that moves most quickly among people living in (53) conditions, hence, it is likely to attack armies.
(54) the nineteenth century there were five widespread outbreaks of influenza. The last of the five (55) in 1889 and marked the beginning of the story of influenza in our time.
(56) the recent outbreak, it started in Asia.
For more than forty years before that outbreak, influenza had steadily (57) and was believed to be dying out. A new group of outbreaks was (58) by the great outbreak of 1889-1890 and for the next quarter of a century influenza remains a constant threat.
In April 918 flu broke among American troops stationed in France. It quickly spread through all the (59) but caused relatively few deaths. Four months later, however, a second outbreak started which (60) to be a killer. It killed not only the old and already sick but also healthy young adults.
It (61) through every country in the world, only a few distant islands in the South Atlantic and the Pacific remaining
(62) . It brought the life of whole countries to stop, food (63) stopped and work loss was very great.
Before the great outbreak ended, it had killed (64) 15 million people. Thereafter, there have been several great outbreaks throughout the world. It is thus (65) that influenza is a terrible infection that we have to pay more attention to.
请在（51）处填写正确答案。 A．by
B．on
C．to
D．with
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