Find the missing element in the following financial goal: “I plan to buy a mobile phone which costs ￥1500 by saving ￥75 from each paycheck（薪水）.”

Find the missing element in the following financial goal: “I plan to buy a mobile phone which costs ￥1500 by saving ￥75 from each paycheck（薪水）.”
A.specific
B.measurable
C.realistic
D.time-bound
正确答案：time-bound