单项选择题 The transmission time duration of a single pulse of radio-frequency energy is a function of the（）.

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（）.