215. When the changing of a VHF channel / frequency is accepted，say _______.
举一反三
- When it is advisable to change to another VHF channel, for example channel 15, you should say:
- 196. When another calling channel/frequency is available，do not use ______ or other safety frequencies to make a transmission.
- The DME frequency band is: A: UHF B: VHF C: FM D: HF
- _______ refer to words that co-occur with high frequency and have been accepted as ways for the use of words.
- Collocations refer to words that co-occur with high frequency and have been accepted as ways for the use of words. ( )