CCB-Ⅱ型制动机ERCP故障时，会自动由模块来代替其功能

A. the boundary between polar air and equatorial air
B. the boundary region between the two monsoons
C. the region between the two trade wind systems centred on the heat equator
D. a region of calm winds and layer type clouds with much haze

A. caused
B. not caused

A. are caused by a large difference in mean temperature in the horizontal
B. are located above the tropopause
C. only occur in the troposphere
D. have a speed in excess of 80 kt