HTML 按钮居中：使用 Flexbox 实现水平垂直居中

<div class='call-to-action-area gray-bg ptb-60'>
        <div class='container'>
			<div class='form-group'>
                <label></label>
                <textarea class='form-control' id='chat-gpt-input' placeholder='输入问题' rows='3' resize='none' style='width: 100%; margin: 0 auto; background-color: #f4f4f4; color: #333; border: 1px solid #ccc; border-radius: 12px;'></textarea>
            </div>
			<div class='call-to-action'>
                <a onclick='callCHATGPT()' class='btn btn-large' href='#' style='background-color: #4cae4c; color: #fff; font-weight: bold; border-radius: 5px; padding: 10px 20px; border: none; box-shadow: none; text-decoration:none;' onmousedown='this.style.backgroundColor='#3c903c'' onmouseup='this.style.backgroundColor='#4cae4c''>回答</a>
                <a onclick='clearTextArea()' class='btn btn-large' href='#' style='background-color: #d9534f; color: #fff; font-weight: bold; border-radius: 5px; padding: 10px 20px; border: none; box-shadow: none; text-decoration:none; margin-left: 20px;' onmousedown='this.style.backgroundColor='#c9302c'' onmouseup='this.style.backgroundColor='#d9534f''>清空</a>
			</div>
			<div class='form-group'>
                  <label></label>
                  <textarea class='form-control' id='chatgpt-response' placeholder='长途访问，请耐心等待回答 Ai生成它很快，但是由于网络问题我们需要等待，通常内容越长等待越久 如果长时间没反应请刷新页面重试' rows='26' resize='none' style='width: 100%;height: auto; margin: 0 auto; background-color: #f4f4f4; color: #333; border: 1px solid #ccc; border-radius: 10px; overflow: scroll;'></textarea>
            </div>
		</div>
        <style>
            .call-to-action {
                display: flex;
                justify-content: center;
                align-items: center;
            }
        </style>
</div>
<p>将class为'call-to-action'的div元素的样式设置为：</p>
<pre><code class="language-css">.call-to-action {
    display: flex;
    justify-content: center;
    align-items: center;
}
</code></pre>
<p>这将使其中的两个a标签按钮水平居中并垂直居中。</p>