（）we stand away from the church bell, it takes time for the sound waves to each us.

单项选择题Before（）,a station shall take precautions to ensure that its emission will not interfere with transmission already in progress.

A.transmit
B.to transmitting
C.transmitting
D.in transmitting

单项选择题The emergency communication set’s transmitter should not be tested except when（）by a public radio inspector.

A.inspecting
B.inspected
C.inspects
D.having inspected

单项选择题Which expression has the different meaning from entry into force ? “entry into force” means is（）.

A.coming into effect
B.moving to full effect
C.being based on force
D.coming into force

单项选择题Radar bandwidth is normally（）to the range scale and the associated pulse length.

A.fixed
B.matched
C.fitted
D.equal

单项选择题A rectangular area is described in degrees of latitude and longitude from the latitude and longitude of the southwest corner of（）.

A.square
B.triangle
C.circle
D.rectangle