var student =  Array(
     ['小A','女',21,'大一'],  ['小B','男',23,'大三'],

     ['小C','男',24,'大四'],  ['小D','女',21,'大一'],

     ['小E','女',22,'大四'],  ['小F','男',21,'大一'],

     ['小G','女',22,'大二'],  ['小H','女',20,'大三'],

     ['小I','女',20,'大一'],  ['小J','男',20,'大三'],
     );
     alert(student.length);
    for(i=0;i<10;i++){
        if((student[i][1]=="女")&&(student[i][3]=="大一")){
            document.write(student[i][0]+"<br>");
        }
    }