What is the appropriate tone for the passage below?

While greatly influenced by the writings of the ancient Greeks and Romans, Leonardo, unlike many of his contemporaries, saw the limitations of seeking the truth solely in those writings or the Bible. Instead, he took the startling approach of actually observing nature and asking deceptively simple scientific questions like, "How do birds fly?" To finish the bill, he then systematically recorded their solutions in his sketches.
a.
Angry
c.
Happy
b.
Sarcastic
d.
Confused