<p> 以下文件操作方法中，打开后能读取CSV格式文件的选项是：( )</p>
<p> fo = open("123.csv","w")</p>
<p> fo = open("123.csv","x")</p>
<p> fo = open("123.csv","a")</p>
<p> fo = open("123.csv","r")</p>
青云测评
