单项选择题

The author mentioned the tornado in Edmonton, Canada in order to ______.

A．explain different types of weather
B．show that tornadoes occur frequently in Canada
C．indicate the tornado are common in summer
D．give an example of a damaging storm

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热门试题

单项选择题

The word they in line 11 refers to ______.

A．models
B．conditions
C．events
D．regions

单项选择题

Why does the author state in line 9 that observations are taken just once every twelve hours

A．to show why the observations are of limited value.
B．to compare data from balloons and computers,
C．to give an example of international cooperation,
D．to indicate that the observations are timely.