Final answer:
Montag and Mildred's relationship in 'Fahrenheit 451' is estranged and characterized by emotional distance, with their inability to answer whether they are happy revealing a deep disconnect between them.
Step-by-step explanation:
In the last half of Part One of Fahrenheit 451, Montag and Mildred's relationship is revealed to be estranged and characterized by a significant emotional distance. The pivotal question that Montag asks Mildred, which neither of them knows the answer to, is "Are you happy?" The inability to answer this question indicates a profound disconnect not only with each other's emotions, but also with their own internal states. This thematic element of happiness and emotional disconnect ties back to the earlier moment in Part One of the novel, where Clarisse asks Montag if he is happy and later performs the dandelion test, which already suggested the absence of true love or happiness in Montag's life.