单项选择题
A.a high-pressure area
B.pressure difference over horizontal distance
C.pressure difference over time
D.vertical pressure variation
单项选择题 On what does the operation of an aneroid barometer depend?（）
单项选择题 MODERATE WAVES，TAKING A MORE PRONOUNCED LONG FORM；MANY WHITE HORSES ARE FORMED.THIS sea condition is likely to be termed（）.
单项选择题 In the Northern Hemisphere，winds veering sharply to the west or northwest with increasing speed are indications that a（）.