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Correction status：qualified
Teacher's comments：
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>2019-3-25 作业</title>
<script type="text/javascript">
//if else语句判断学习成绩
var a = 25;
if (a>=90){
alert('优秀!');
}else if(a<90 && a>=80){
alert('良好!');
}else if(a<80 && a>=70){
alert('良');
}else if(a<70 && a>=60){
alert('及格');
}else{
alert('不及格');
}
//if else语句判断闰年
var years = 2001;
if(years%4==0 && years%100==0 && years%400==0){
document.write('这是闰年')
}else if(years%4==0 && years%100!=0){
document.write('这是闰年')
}else{
document.write('这不是闰年')
}
</script>
</head>
<body>
</body>
</html>
