单项选择题
Prior to reading an aneroid barometer，you should tap the face lightly with your finger to（）.
A.expose any loose connections B.demagnetize the metal elements C.bring the pointer to its true position D.contract and expand the glass face
单项选择题 Pressure gradient is a measure of（）.
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（）.
