1. 人质
    A hostage is someone who has been captured by a person or organization and who may be killed or injured if people do not do what that person or organization demands.

    e.g. It is hopeful that two hostages will be freed in the next few days.
           有两名人质可望在几天后获释。

2. 被扣作人质
    If someone is taken hostage or is held hostage, they are captured and kept as a hostage.

    e.g. He was taken hostage while on his first foreign assignment as a television journalist.
           他第一次作为电视记者出国采访时就被扣作人质。

3. 受限制的人;不由自主的人
    If you say you are hostage to something, you mean that your freedom to take action is restricted by things that you cannot control.

    e.g. With the reduction in foreign investments, the government will be even more a hostage to the whims of the international oil price...
           随着外资的减少，政府将更加受制于起伏不定的国际油价。
    e.g. Wine growers say they've been held hostage to the interests of the cereal and soybean farmers.
           葡萄种植兼酿酒者说他们一直都为谷物和大豆种植者的利益所绑架。