效果如下图
代码：
<!DOCTYPE html>
<html>
<head>
<title>Bootstrap 实例</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="bootstrap.min.css">
<script src="jquery.min.js"></script>
<script src="popper.min.js"></script>
<script src="bootstrap.min.js"></script>
<style>
body {
padding: 20px 100px;
}
.form-inline-multiple {
display: flex;
align-items: center;
justify-content: space-between;
}
</style>
</head>
<body>
<div class="container">
<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#myModal">打开模态框</button>
<div class="modal fade" id="myModal">
<div class="modal-dialog">
<div class="modal-content">
<div class="modal-header">
<h4 class="modal-title">模态框头部</h4>
<button type="button" class="close" data-dismiss="modal">×</button>
</div>
<div class="modal-body">
<form action="">
<div class="form-group">
<label for="email">Email address:</label>
<div class="form-inline form-inline-multiple">
<input type="text" class="form-control mr-sm-2" style="width: 73%;">
<input type="text" class="form-control" style="width: 25%;" value="选择题一">
</div>
</div>
<div class="form-group">
<label for="pwd">Password:</label>
<input type="password" class="form-control" placeholder="Enter password" id="pwd">
</div>
<button type="submit" class="btn btn-primary">Submit</button>
</form>
</div>
<div class="modal-footer">
<button type="button" class="btn btn-secondary" data-dismiss="modal">关闭</button>
</div>
</div>
</div>
</div>
</div>
</body>
</html>