如果选择了特定活动，则检查单选按钮

<input type="radio" id="activity1" name="activity" value="activity1">
<label for="activity1">活动1</label>

<input type="radio" id="activity2" name="activity" value="activity2">
<label for="activity2">活动2</label>

<input type="radio" id="activity3" name="activity" value="activity3">
<label for="activity3">活动3</label>

// 获取特定活动选择框和单选按钮组
const activitySelect = document.getElementById("activitySelect");
const radioButtons = document.getElementsByName("activity");

// 监听特定活动选择事件
activitySelect.addEventListener("change", function() {
  const selectedActivity = activitySelect.value;

  // 遍历单选按钮组，根据选择的活动值选中对应的单选按钮
  for (let i = 0; i < radioButtons.length; i++) {
    if (radioButtons[i].value === selectedActivity) {
      radioButtons[i].checked = true;
      break;
    }
  }
});