Which sentence correctly uses the possessive form
AThe Chairman of the Boards microphone was turned off, so we could not hear what he said.
BThe Chairman's of the Boards microphone was turned off, so we could not hear what he said.
CThe Chairman of the Board's microphone was turned off, so we could not hear what he said.
DThe Chairman of the Boards' microphone was turned off, so we could not hear what he said.
AThe Chairman of the Boards microphone was turned off, so we could not hear what he said.
BThe Chairman's of the Boards microphone was turned off, so we could not hear what he said.
CThe Chairman of the Board's microphone was turned off, so we could not hear what he said.
DThe Chairman of the Boards' microphone was turned off, so we could not hear what he said.