line

html,
body,
svg {
  height: 100%;
}

<svg viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg">
  <line x1="0" y1="80" x2="100" y2="20" stroke="black" />

  <!-- 如果不指定描边颜色，则无法看见线条 -->
</svg>