显微镜下可以清晰地看到细胞壁周围有一个环状结构。

Under the microscope, you can clearly see an ___annulus surrounding the cell wall.

这个戒指的形状是一个圆环，由两个同心圆组成。

The ring's shape is an ___annulus, formed by two concentric circles.

日环食发生时，我们看到月亮周围形成了一个明亮的环形光晕。

During the annular eclipse, we saw a bright ___annulus around the moon.