Which of Gibson's Statements Indicates That He Is Engaging in Hypothetical-Deductive

Multiple Choice

Which of Gibson's statements indicates that he is engaging in hypothetical-deductive reasoning?

A) "I can still hear the sound of that guitar after the string has been strummed."
B) "A guitar is just a larger version of a mandolin."
C) "I bet that my guitar looks exactly like the one you have."
D) "If the length of a guitar string matters, then a short string should produce a different sound than a long string."