单项选择题

Generally，what is used to inflate liferafts?（）

A.non-toxic gas
B.Oxygen
C.Hydrogen
D.Helium

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单项选择题

Generally speaking，you should expect to find low atmospheric pressure prevailing in the earth’s（）.

A.equatorial area
B.polar regions
C.mid-latitudes
D.All of the above

单项选择题

Generally speaking，in the Northern Hemisphere，when winds are blowing from between SE and SW the barometric reading（）.

A.makes no change at all
B.is somewhat lower than it would be for winds from a northern quadrant
C.is uncertain and may fluctuate by increasing and decreasing
D.is somewhat higher than it would be for winds from the northern quadrant