There are multiple ways to achieve the various endings, especially regarding the first conversation segment, but I've created a guide that will help you obtain your desired ending! This version will give you hints to obtain each ending without explicitly telling you what options you need to select.

Ending D: 

Do not engage in conversation at all, end conversation early, or let the timer run out before asking a critical question

Ending C: 

Pick topics that show more interest/engagement in Aeda herself. After asking a critical question, stay behind, and try to appeal to Aeda emotionally.

Ending B: 

Pick topics that show more interest/engagement in Aeda herself. After asking a critical question, stay behind, and reason with Aeda using logic.

Ending A: 

Pick topics that show more interest/engagement in Aeda herself. After asking a critical question, opt to go watch the sunrise.