为什么在table里放<hr/>在网页上显示的分割线都聚在一起了？
<!DOCTYPE HTML>
<html>
<head>richengbiao</head>
<hr/>
<body>
<table>
<tr>
<th>11</th>
<th>12</th>
<th>13</th>
<th>14</th>
<th>15</th>
<th>16</th>
<th>17</th>
</tr>
<hr/>
<tr>
<td>one hour:</td>
<td>one hour:</td>
<td>one hour:</td>
<td>one hour:</td>
<td>one hour:</td>
<td>one hour:</td>
<td>one hour:</td>
</tr>
<hr/>
<tr>
<td>half an hour:</td>
<td>half an hour:</td>
<td>half an hour:</td>
<td>half an hour:</td>
<td>half an hour:</td>
<td>half an hour:</td>
<td>half an hour:</td>
</tr>
<hr/>
<tr>
<td>three hours:nomal class</td>
<td>three hours:nomal class</td>
<td>three hours:nomal class</td>
<td>three hours:nomal class</td>
<td>three hours:nomal class</td>
<td>three hours:nomal class</td>
<td>three hours:nomal class</td>
</tr>
<hr/>
<tr>
<td>one or tow hour:</td>
<td>one or tow hour:</td>
<td>one or tow hour:</td>
<td>one or tow hour:</td>
<td>one or tow hour:</td>
<td>one or tow hour:</td>
<td>one or tow hour:</td>
</tr>
</table>
</body>
</html>
