单项选择题
Loran-C uses the multiple pulse system because（）.
A.Less signal energy is necessary for receiver operation B.More signal energy is available at the receiver C.It significantly increases the peak power D.It increases the signal capacity
单项选择题 Loran-C is which type of system（）.
单项选择题 In using Loran-C，skywave reception gives greater range but is（）.
单项选择题 If the radio signal ground wave extends out for less distance than the minimum skywave distance，there is an area in which no signal is received．This is called the（）.
