支票使用前一定不要在上面签名字。
B：To prevent someone from getting it and taking the money, right?
这是为了防止有人拿到它把钱取了，对吗？
sign /sa?n/ v. 在……上面签名；签署
prevent /pr??vent/ v. 防止，预防；阻止
■ prevent sb/sth (from) doing (sth) 表示“防止或制止……做（某事）；阻止……发生”。例如：His back injury may prevent him from playing in tomorrow's game.（他背上的伤让他不能参加明天的比赛。）
给支票背书 endorse a check
A：Why does the bank ask customers to endorse checks?
银行为什么要求客户给支票背书呢？
B：The bank asks the clients to sign his or her name on the back of the check to show that it's correct.
银行要求客户在支票背面签名是要证明支票上的内容是正确的。