The answer is the third option, C. he told the disciples about future events, including his second return.
In the bible, you can derive two different definition of prophet, one being the prophet of mankind, and a prophet of GOD.
Most of the answers can work, however, as Jesus is the son of GOD (and so a prophet of GOD), then the answer is the words he spoke were from GOD, as it encompasses all the other aspects (being the most broadest).
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