为什么我多次点提交，就点出了mooc网的界面

<form>
   <label for="male">慢跑</label>
  <input type="checkbox" name="gender" id="male" />
  <br />
  <label for="female">登山</label>
  <input type="checkbox" name="gender" id="female" />
  <br />
  <label for="email">篮球</label>
  <input type="checkbox" name="basktball" id="email" >
  <br>
  <input type="submit" name="submit" value="提交" >
</form>