which one of the following statements about HF is correct
A、HFisusedforlong-rangecommunication.
B、HFsignalsaresubjecttothelineofsight.
C、HFradiowavescannottravelstraightforward.
D、HFisusedbymostoftheenrouteairtrafficunits.
发布时间：2024-09-27 05:40:16
