要使用CSS在 flex-basis属性上实现动画，您可以尝试运行以下代码
<!DOCTYPE html>
<html>
<head>
<style>
.box {
display: flex;
background-color: green;
}
.box > div {
background-color: white;
text-align: center;
line-height: 40px;
font-size: 25px;
width: 100px;
margin: 5px;
}
div {
animation: myanim 4s infinite;
}
@-webkit-keyframes myanim {
50% {
flex-basis: 100px;
}
}
</style>
</head>
<body>
<h1>Quiz</h1>
<div class = "box">
<div>Q1</div>
<div>Q2</div>
<div>Q3</div>
<div style = "flex-basis: 350px">Q4</div>
<div>Q5</div>
<div>Q6</div>
<div>Q7</div>
<div>Q8</div>
<div>Q9</div>
</div>
</body>
</html>