2._____ clouds form at heights of 2,000 meters or less.
A.Cumulus
B.Cirrus
C.Cirrostratus
D.Altocumulus
Erosion caused by waves can destroy ____.
A.Rocky shorelines
B.Sandy shorelines
C.Beaches
D.All of the above
The horizontal distance between the highest or the lowest points of two successive waves is the _____.
A.Crest
B.Tidal range
C.Trough
D.Wavelength
When the top of a wave moves faster than the bottom of a wave,the wave collapses,forming a(n) _____.
A.Trough
B.Upwelling
C.Breaker
D.Density current