This should be under a Science not history, but the answer is
D. visual perception
Answer:
Bloomberg took the brunt of the fire after spending his way onto the debate stage for the first time, but everyone had to take their turn playing offense and defense. Warren critiqued every other candidate’s health care plan in a single answer, injecting a rush of energy into her campaign. Pete Buttigieg and Amy Klobuchar continued a running battle that has built over several debates, while Biden lit into Bloomberg over Obamacare and Sanders faced questions about his policy disagreements with a powerful Nevada labor union.
(If you want I can make the words less complicated or advanced and add sentences.)
The main factions were the Radicals and Conservatives.
