html - 了解表属性的特殊性

Question

"A selector's weighting is evaluated based on the components that make it up, with id's given a weighting of 100, classes with a weighting of 10, and element selectors with weighting of 1."

根据这个 th 应该权重 1 而 tr:nth-child(2n+1) 由于伪类应该权重 11。但是在浏览器中显示时使用 th 的背景颜色。你能解释一下为什么吗？

table {
  margin-left: 20px;
  margin-right: 20px;
  border: thin solid black;
  caption-side: bottom;
  border-collapse: collapse;
}

td,
th {
  border: thin dotted gray;
  padding: 5px;
}

caption {
  font-style: italic;
  padding-top: 8px;
}

td.center,
th.center {
  text-align: center;
}

td.right,
th.right {
  text-align: right;
}

th {
  background-color: #cc6600;
}

tr:nth-child(2n+1) {
  background-color: #fcba7a;
}

<table>
  <caption>The cities I visited on my Segway'n USA travels</caption>
  <tr>
    <th>City</th>
    <th class="center">Date</th>
    <th class="center">Temprature</th>
    <th class="right">Altitude</th>
    <th class="right">Population</th>
    <th class="center">Dinner Rating</th>
  </tr>
  <tr>
    <td>Walla Walla, WA</td>
    <td class="center">June 15th</td>
    <td class="center">78</td>
    <td class="right">1,204 ft</td>
    <td class="right">29,686</td>
    <td class="center">4/5</td>
  </tr>
  <tr class="cellcolor">
    <td>Magic City, ID</td>
    <td class="center">June 25th</td>
    <td class="center">74</td>
    <td class="right">5,312 ft</td>
    <td class="right">50</td>
    <td class="center">3/5</td>
  </tr>
  <tr>
    <td>Bountiful, UT</td>
    <td class="center">July 10th</td>
    <td class="center">91</td>
    <td class="right">4,226 ft</td>
    <td class="right">41,173</td>
    <td class="center">4/5</td>
  </tr>
  <tr class="cellcolor">
    <td>Last Chance, CO</td>
    <td class="center">July 23rd</td>
    <td class="center">102</td>
    <td class="right">4,780 ft</td>
    <td class="right">256</td>
    <td class="center">3/5</td>
  </tr>
  <tr>
    <td>Truth Or Consequences, NM</td>
    <td class="center">August 9th</td>
    <td class="center">93</td>
    <td class="right">4,242 ft</td>
    <td class="right">7,289</td>
    <td class="center">5/5</td>
  </tr>
  <tr class="cellcolor">
    <td>Why, AZ</td>
    <td class="center">August 18th</td>
    <td class="center">104</td>
    <td class="right">860 ft</td>
    <td class="right">480</td>
    <td class="center">3/5</td>
  </tr>
</table>

Answer 1

th和tr是两个不同的元素，不会互相影响。