阅读下段代码import java.util.Enumeration;import java.util.Properties;public class Demo { public static void main(String[] args) {Properties p = new Properties();p.setProperty("userame", "tom");Enumeration names = p.propertyNames();while (names.hasMoreElements()) {String key = (String) names.nextElement();String value = p.getProperty(key);System.out.println(key + " = " + value);} }}下列选项中,哪一个是程序执行后的结果( )

A. key = tom
B. username = tom
C. username tom
D. 编译失败