5．Why do you have to...?
    你為什么要……?
    Why do you have to tell her the truth?
    你為什么要告訴她真相?
    Why do we have to help you.
    還有為什么讓我們幫助你。
    Those are common manifestations, which is why you do have to remain vigilant.
    這些現(xiàn)象表明，你必須保持警醒。
    However, you need to do some calculations and you may want to understand whyyou have to do so.
    但是，您需要做一些計(jì)算，您可能想明白你為什么要這樣做。