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问题 不定项选择

在空中同一高度处有A、B两个小球，某一时刻小球A以初速度vA水平向右抛出，同时小球B以初速度vB向上抛出，不计空气阻力。则两球在空中运动的过程中

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A．小球B做匀变速运动，小球A做变加速曲线运动

B．相同时间内A、B两球速度的变化不相等

C．A．B两球的动能都随离地竖直高度均匀变化

D．A、B两球可能在空中相碰

答案

答案：C

单项选择题

在关系数据库中，用来表示实体间联系的是（）。

A．网状结构

B．树状结构

C．属性

D．二维表
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填空题


Health officials in western Siberia are to begin in slaughter of thousands of birds today after identifying Russia’s first outbreak of a bird flu strain that can be fatal in humans. Doctors in neighboring Kazakhstan have also (1) that a 19-year-old poultry worker (2) admitted to hospital with (3) of bird flu, only to be diagnosed (4) double pneumonia.
The H5N1 strain of avian (5) has killed 60 people (6) 2fib in Vietnam, Thailand, Cambodia and Indonesia, but has rarely been found in birds or humans (7) Asia.
Health officials (8) that HSN1 is infecting migrating birds, which could spread the (9) into Europe. Earlier this year China registered the first outbreak of H5N1 (10) wild birds, some of which (11) to breeding grounds in Siberia. These birds could come (12) contact with others flying to Europe and North America.
Russia’s (13) began in the Novosibirsk (14) , about 1,750 miles (15) of Moscow in the Asian part of Russia, early last month, but the veterinary service (16) the virus only last week. Valery Mikheyev, the chief sanitary doctor of Novosibirsk, said that teams had been (17) the (18) birds and supervising the slaughter in13 (19) villages. He said, "The state of (20) of the inhabitants of these areas gives (21) cause for alarm. Up to 6,000 people are being (22) per day.
The virus seems to have (23) only private farms that let (24) mix with wild birds. Further outbreaks were registered in the Omsk and Altai regions, but the strain had (25) to be determined, Russia’s Emergency Situations Ministry said.
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