The tone of the text is sarcastic. (Option D). The choice of words that betray this fact are: " but whether relating to the past, present, or future, could not easily be determined"
Tone in literature is a word that is used to describe the attitude that the author exhibits in relation to the text or story. This is deduced form the choice of word that the write uses.
Hence, it is right to state that the above excerpt bear a sarcastic tone.
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