What Is the Central Concept Behind the Idea of Ego

What is the central concept behind the idea of ego depletion?

A) People are unable to focus on a task when they are trying to keep distracting thoughts out of consciousness.
B) Ego strength can be depleted by extensive use of self-control.
C) Over time across the lifespan,people lose the majority of their cognitive faculties.
D) When people are in a state of high self-awareness,they become less focused on their own goals and attitudes.