Since Lucy has some life goals that she would like to attain, she needs to attach a goal cost to each of them. Goal cost generally refers to the amount of resources that a person has to expend in order to achieve it.
From the available options, the best reason as to why she would need to do this, based on the definition previously given, would be due to (A) she wants to identify the amount of money, time, and effort required to realize her goals.