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<meta charset="UTF-8">
<title>Empty ruby text container</title>
<link rel="author" title="Xidorn Quan" href="https://www.upsuper.org">
<div style="font-size: 64px; line-height: 5">a<ruby><rb>b</rb><rtc><rt></rt></rtc><rt>c</rt></ruby>d</div>