How Would One Address the Question of How Attention Shifts

How would one address the question of how attention shifts from one thing to another?

A) By studying the difference between the unconsciously mediated attentional processes and those that are controlled by more automatic process.
B) By studying the difference between the consciously mediated attentional processes and those that are controlled by more automatic process.
C) By studying the differences in the ability to concentrate in individuals.
D) By analyzing different memory processes and how they are affecting ones ability to concentrate.