我制作了一个带有 flex 属性的导航栏。现在我希望向导航栏中的元素添加一个下拉菜单，但它没有按预期工作。
@font-face {
font-family: Oxygen;
src: url('https://fonts.googleapis.com/css?family=Oxygen');
}
body{
margin: 0;
}
nav {
background-color: #f8f8f8;
display: flex;
justify-content: space-between;
}
nav ul {
height: 50px;
display: flex;
align-items: center;
justify-content: flex-start;
margin: 0;
}
nav a {
text-decoration: none;
color: #777;
padding: 15px;
font-family: sans-serif;
font-size: 18px;
}
nav a:hover {
color: #000;
}
.logo a {
font-size: 25px;
}
nav ul {
list-style: none;
}
ul.drop-menu li {
display: none;
list-style: none;
}
li:hover > ul.drop-menu …