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index 1f02ca5..85ef448 100644
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@@ -25,5 +25,7 @@
 <h2>課題３</h2>
 <p>鎌倉幕府は<span class="check">1192</span>年、</p>
 
+<h2>課題４</h2>
+<p>鎌倉幕府は<span class="check" id="box" onclick="red()">1192</span>年、</p>
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 </html>