有理数包含正数、负数和　____ ．

增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。

删除：把多余的词用斜线（\）划掉。

修改：在错的词下划一横线，并在其下面写出修改后的词。

注意：1）每处错误及其修改均仅限一词；

2）只允许修改10处，多者（从第11处起）不计分。

    I was always afraid of water because I nearly get drowned when I was young. As I grew old, this fear was still with me. However, my attitude to water changed last summer. One day, several classmates asked me lean to swim with them, and of course, I said no. But they were quite determined and repeated explained the benefits of swimming for me. So finally I agreed to give them a try. You can imagine what scared I was when I first had stepped into the swimming pool. But gradually, I found it great funs in the water. Now I'm no longer a gird live in fear of water.

王某正在美国留学，拟购买一台手提电脑，可以用美元现金或国内银行发行的信用卡结算。如王某使用信用卡，国内银行按消费时的汇率自动将美元折算为人民币结算。现预期人民币将持续升值。假设价格和其他因素不变，王某的理性决策是（  ）