two-fold symmetry

例句：

1. 1. The two-fold symmetry of the butterfly's wings is a wonder to behold.
   蝴蝶翅膀的双折对称令人惊叹。
2. 2. The two-fold symmetry of the flower's petals is a testament to nature's beauty.
   花朵花瓣的双折对称是大自然之美的见证。
3. 3. The two-fold symmetry of the crystal structure is responsible for its unique optical properties.
   晶体结构的双折对称是其独特光学属性的原因。