css实现如图所示的右下拉菜单，（想要HTML和css的代码），挺急的，

https://v4.bootcss.com/docs/components/dropdowns/ 有类似的

Bootstrap3 没有这种布局但是4有

我想要这样css的代码

我调了几遍，但总是调不出来

你不会用Bootstrap 么？

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style type="text/css" >
			.list{
				width: 100px;
				height: 40px;
				background-color: blue;
				border: 1px solid #fff;
				color: #fff;
				text-align: center;
				line-height: 40px;
				position: relative;
			}
			
			.list:hover .items{
				display: block;
			}
			
			.item{
				width: 100px;
				height: 40px;
				background-color: blue;
				border: 1px solid #fff;
				color: #fff;
				text-align: center;
				line-height: 40px;
			}
			
			.item:hover{
				background-color: yellow;
				color: #000;
			}
			
			.items{
				display: none;
				position: absolute;
				top: 0px;
				left: 100px;
			}
			
		</style>
	</head>
	<body>
		<div style="margin: 50px;" >
			<div class="list" >
				a
				<div class="items" >
					<div class="item" >a1</div>
					<div class="item" >a2</div>
					<div class="item" >a3</div>
				</div>
			</div>
			<div class="list" >
				b
				<div class="items" >
					<div class="item" >b1</div>
					<div class="item" >b2</div>
					<div class="item" >b3</div>
				</div>
			</div>
			<div class="list" >
				c
				<div class="items" >
					<div class="item" >c1</div>
					<div class="item" >c2</div>
					<div class="item" >c3</div>
				</div>
			</div>
		</div>
	</body>
</html>