Lin Xun isn't the one lusting after Rona anymore. It seems to be the other way around now.
According to the text description, it was only after Rona saw that he could inhabit the Shell of a university professor and therefore access many different personas, that she developed a strong curiosity towards him.
In essence, in Rona's eyes, he was no different from that 'Nano-bio Armor'. The only difference might be that her curiosity for him is perhaps a bit more intense.
As per usual, he automatically ignored the first two options and chose the third.
[After a moment of hesitation, you honestly say that your previous confession of love was because you were captivated by its charm and your blood was running high at the moment. Looking back, you believe your behavior was somewhat impulsive.]
[However, if Rona would continue to accompany you, exploring the journey ahead and clearing the entire Association Building, you would not be opposed to agreeing to her proposal.]