The answer is
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Property, plant and equipment</span>
The type of channel that speaker one and speaker two use in their communication would be auditory - b.
The fact that we're talking about "speaker" 1 and "speaker" 2 implies already the fact that both of them are talking and this then implies that they are using the auditory channel of communication.
I believe it’s “if something takes energy IN then it must give energy OUT. “
I hope this helped! :-)