答案

BCDCC
DCBBB
CABCA
BACDC
AB

超出部分效果
101
x<20 || x<=18 || x<19
<input type="checkbox" name="check">
onmouseover
<hr>
h1
1

2、var a=[1,2,3,4,5,6,7,1,2,3,4,5,6,7,1,2,3,4,5,6,7] 
var b=[  ]

for (var i=0 ;i<a.length ;i++) {
    var status = 0;
    for (var j=0 ;j<b.length ;j++) {
         if(a[i]==b[j]){
             status = 1;
             break;
         } 
     } 
    if(status == 0){
    b.push(a[i])
    }
}

for(var x in b){
    document.write(b[x]+"&nbsp;")
}

3、

function wnl() {

var time = new Date();
var year = time.getFullYear();
var month = time.getMonth() + 1;
var day = time.getDate();
var hour = time.getHours();
var min = time.getMinutes();
var sec = time.getSeconds();
var time_str = year + "年" +
month + "月" +
day + "日" +
"&nbsp;&nbsp;&nbsp;" +
hour + ":" +
min + ":" +
sec;
document.getElementById("time").innerHTML =
time_str;
}

var x = window.setInterval("wnl()", 1000);