When a hurricane passes into high latitudes over colder water and the source of heat is disrupted，the storm assumes the characteristics of（）.

单项选择题What kind of pressure systems travel in easterly waves（）.

A.High pressure
B.Low pressure
C.Subsurface pressure
D.Terrastatic pressure

单项选择题What kind of conditions would you observe as the eye of a storm passes over your ship’s position（）.

A.Huge waves approaching from all directions，clearing skies，light winds，and an extremely low barometer
B.Flat calm seas，heavy rain，light winds，and an extremely low barometer
C.Flat calm seas，heavy rain，light winds，and high pressure
D.Huge waves approaching from all directions，clearing skies，light winds，and high pressure

单项选择题What is the first visible indication of the presence of a tropical cyclone or hurricane（）.

A.Stratocumulus clouds or strange birds
B.Rain and increasing winds
C.An exceptionally long swell
D.Dark clouds and the“bar”of the storm

单项选择题Two well-developed high pressure areas may be separated by a（）.

A.Hill of low pressure
B.Trough of low pressure
C.Valley of low pressure
D.Ridge of low pressure

单项选择题Tropical cyclones are classified by form and intensity.Which system does not have closed isobars（）.

A.Hurricane
B.Tropical disturbance
C.Tropical depression
D.Cyclone