单项选择题
The transmission time duration of a single pulse of radio-frequency energy is a function of the（）.
A.persistence B.pulse repetition rate C.pulse length D.resolution
单项选择题 You are using a radar in which your own ship is shown at the center，and the heading flash always points to 0°. If bearings are measured in relation to the flash，what type of bearings are produced?（）.
单项选择题 Compass deviation is caused by（）.
单项选择题 Compass error is equal to the（）.
