单选题 .  A credit card can be useful. You could take it into a store and buy a television set or new furniture or clothing or anything you want. All you would have to do is to sign your name and take what you want out of the store without paying cash.
    But there is a problem with the cards—they can be financial poison. These cards are just like the poison we use on insects. If we use them carefully, they can be helpful; but if we use them too much, they can kill us. These cards can kill us financially just as real poison can kill our body.
    For any money that the user does not pay each month, the credit card company charges a percentage of that amount in interest (利息). The interest is added every month, so a bill that is not paid gets bigger and bigger.
    Over 10 percent of the families in the United States are "overextended". That is, they have more debts on their credit cards than they can pay.
    Credit cards can be used for almost anything that money can buy. And they can even be used to pay for funerals. For some credit card users, a funeral may be the only solution to the debt problems they have caused for themselves by using credit cards.1.  A credit card is so useful in daily life that if you have one ______.